A zika virus chimeric polyepitope comprising non-structural proteins and its use in an immunogenic composition

ABSTRACT

The present invention is directed to a Zika virus (ZIKV) chimeric polyepitope comprising non-structural proteins and its use in an immunogenic composition. The present invention provides means, in particular polynucleotides, vectors and cells expressing said chimeric polyepitope. The present invention also relates to a composition or a vaccine comprising at least one of said polyepitope, polynucleotide, vector or host cell for use in the prevention of a ZIKV infection in a human subject, or for use in the prevention of ZIKV and dengue virus (DENV) infections in a human subject.

The present invention is directed to a Zika virus (ZIKV) chimeric polyepitope comprising non-structural proteins and its use in an immunogenic composition. The present invention provides means, in particular polynucleotides, vectors and cells expressing said chimeric polyepitope. The present invention also relates to a composition or a vaccine comprising at least one of said polyepitope, polynucleotide, vector or host cell for use in the prevention of a ZIKV infection in a human subject, or for use in the prevention of ZIKV and dengue virus (DENV) infections in a human subject.

Zika virus (ZIKV) is a flavivirus transmitted by Aedes species mosquitoes. It is a single positive-stranded RNA virus closely related to yellow fever virus, dengue virus (DENV) and West Nile virus (Kuno G et al., 1998, J Virol. 72(1):73-83). Initially isolated in the Zika forest in Uganda in 1947 (Dick G W et al., 1952, Transactions of the Royal Society of Tropical Medicine and Hygiene 46(5):509-520), it caused an explosive outbreak for the first time in Yap Island, Federated States of Micronesia (Duffy M R, et al. 2009, The New England journal of medicine 360(24):2536-2543). Subsequent outbreaks with higher number of cases occurred in 2013-2014 in French Polynesia and other South Pacific Islands and more recently in the Americas (Cao-Lormeau V M, et al. 2014, Emerging infectious diseases 20(6):1085-1086; Campos G S, et al. 2015, Emerging infectious diseases 21(10):1885-1886; Dupont-Rouzeyrol M, et al. 2015, Emerging infectious diseases 21(2):381-382; Zanluca C, et al. 2015, Mem Inst Oswaldo Cruz 110(4):569-572; Pacheco O, et al. 2016, Zika Virus Disease in Colombia—Preliminary Report. The New England journal of medicine). Although initially believed to only cause mild, self-limiting disease, a causal relationship between ZIKV and neurological complications, such as Guillain-Barré syndrome or congenital malformations was established only recently, with the 2013 and 2015 outbreaks in French Polynesia and Brazil (Oehler E, et al. 2014 Euro Surveill 19(9); Cao-Lormeau V M, et al. 2016, Lancet 387(10027):1531-1539; Cauchemez S, et al. 2016, Lancet 387 (10033): 2125-2132; Soares de Araujo J S, et al. 2016, Bull World Health Organ 94(11):835-840).

In addition to an enhanced infectivity of the Asian lineage of ZIKV due to a spontaneous mutation in NS1 (Liu Y, et al. 2017, Nature 545 (7655): 482-486), which could explain its recent re-emergence in the Americas (Enfissi A et al., Lancet 387(10015):227-228), one of the most important concerns today is related to the high level of DENV seroprevalence in areas where ZIKV is circulating (Katzelnick L C, et al., The Lancet. Infectious diseases 17(3):e88-e100). Indeed, recent studies have shown that anti-DENV pre-existing antibodies may enhance ZIKV infection and increase disease severity (Dejnirattisai W, et al. 2016 Nat Immunol 17(9):1102-1108; Stettler K, et al. 2016 Science 353(6301):823-826; Paul L M, et al. 2016 Dengue Virus Antibodies Enhance Zika Virus Infection. BioRxiv; Priyamvada L, et al. 2016, Proc Natl Acad Sci USA 113(28):7852-7857; Bardina S V, et al. 2017, Science 356(6334):175-180). Given these constraints, and the lack of appropriate treatment for ZIKV infection, there is an urgent need to develop a vaccine against this infectious disease.

While antibodies against the E protein of DENV or ZIKV were shown to be highly cross-reactive, T cells can be cross-reactive or not, depending on the targeted peptides. A low degree of CD4 T-cell cross-reactivity between DENV and ZIKV was indeed observed in human donors immune to one of these viruses (Stettler K, et al. 2016, Science 353(6301):823-826), whereas DENV/ZIKV cross-reactive and protective CD8 T cells were identified in DENV-immune mice after challenge with ZIKV (Wen J, et al. 2017, Nat Microbiol 2:17036). Considering the sequence identity between DENV and ZIKV for the capsid and envelop structural proteins, and the non-structural proteins NS3 and NS5, that represent the main targets of DENV-specific CD4 and CD8 T cells, respectively, and the protective role of DENV-specific T cells (Weiskopf D et al., Proc Natl Acad Sci USA 2013, 110(22):E2046-2053; Weiskopf D et al., Proc Natl Acad Sci USA 2015, 112(31):E4256-4263, Rivino L & Lim M Q, 2016, Immunology 150(2):146-154), efforts are thus currently directed towards the mapping of T-cell epitopes to design new and more effective vaccines against ZIKV. Predictions of T-cell antigens were conducted by modelling potential epitopes that could bind to different HLA class I or class II alleles, from the ZIKV proteome and by analyzing ex vivo T-cell responses in transgenic mice expressing human HLA-B*0702 and HLA-A*0101 molecules (Wen J, et al. 2017, Nat Microbiol 2:17036, 23-25). Strikingly, DENV/ZIKV cross-reactive T cells were identified in these DENV-immune mice, which could mediate protection against ZIKV infection (Wen J, et al. 2017, Nat Microbiol 2:17036, 23-25). This result is in agreement with concomitant studies demonstrating a protective role for CD8+ T cells in immune protection against ZIKV in mice (Elong Ngono A, et al. 2017, Cell host & microbe 21(1):35-46). However, while these studies have demonstrated a protective role for CD8+ T cells against ZIKV infection in mice, and while several peptides derived from ZIKV have been identified in DENV-naïve and DENV-pre-exposed donors (Grifoni A, et al. 2017, J. Virol. DOI: 10.1128/JVI. 01469-17, posted online on 4 Oct. 2017), the precise identification of the human T-cell epitopes that are unique to ZIKV or shared with DENV is still incomplete. In the present study, the inventors identified these epitopes from blood donors with a history of only ZIKV infection or both DENV and ZIKV infections.

Using PBMCs from Colombian blood donors with previous ZIKV infection, the inventors established the first map of the distribution of ZIKV T-cell epitopes, by quantifying ex vivo IFNγ responses against peptides covering the whole ZIKV proteomic sequence by enzyme-linked immunosorbent spot (ELISPOT) assay. Measurement of the magnitude of T-cell responses (mediated by CD4 and/or CD8 T cells) against these peptides allowed the identification of immunodominant epitopes that induced strong responses in donors carrying specific HLA alleles. More specifically, the inventors showed that the structural proteins C and E and the non-structural (NS) proteins NS1, NS3, NS4B and NS5, in particular the non-structural proteins NS1, NS3 and NS5, contained most of the immunodominant epitopes that induced a strong T-cell response. In donors with a history of DENV infection, the strongest T-cell responses were directed against peptides with a high level of amino acid identity with the four serotypes of DENV, and some matched previously described DENV CD8+ T-cell epitopes, suggesting the activation of cross-reactive T cells. The results of the inventors provided new insights into T-cell responses to ZIKV and identified for the first time in immune individuals, T-cell epitopes that could be used for future ZIKV and DENV vaccine candidates.

The invention thus relates to a chimeric polyepitope comprising (i) at least the following T-cell epitopes of (a) and (b), or (ii) at least the following T-cell epitopes of (a) and (c), or (iii) at least the following T-cell epitopes of (b) and (c):

(a) a T-cell epitope of the non-structural (NS) NS1 protein of a Zika virus (ZIKV) comprising or consisting of an amino acid sequence selected from the group consisting of SEQ ID NOs: 10-12, 14, 15, 17-19, 23, 24 and 78-83, (b) a T-cell epitope of the NS3 protein of a ZIKV comprising or consisting of an amino acid sequence selected from the group consisting of SEQ ID NOs: 28, 29, 31, 33-35, 84 and 85, (c) a T-cell epitope of the NS5 protein of a ZIKV comprising or consisting of an amino acid sequence selected from the group consisting of SEQ ID NOs: 46, 48-50, 52-55, 57-60, 62, 64, 67, 69, 72, 73 and 86-91, or a T-cell epitope variant thereof, which differs from the original amino acid sequence of the T-cell epitope of (a), (b) or (c) by point mutation of one or more amino acid residues and which has at least 90% sequence identity or more than 95% sequence identity or 99% sequence identity with said original sequence.

In a particular embodiment of the invention, the chimeric polyepitope comprises (i) at least the following T-cell epitopes of (a) and (b), or (ii) at least the following T-cell epitopes of (a) and (c), or (iii) at least the following T-cell epitopes of (b) and (c):

(a) a T-cell epitope of the NS1 protein of a ZIKV comprising or consisting of an amino acid sequence selected from the group consisting of SEQ ID NOs: 10-12, 14, 15, 17-19, 23, 24 and 78-83, (b) a T-cell epitope of the NS3 protein of a ZIKV comprising or consisting of an amino acid sequence selected from the group consisting of SEQ ID NOs: 28, 31, 33-35, 84 and 85, (c) a T-cell epitope of the NS5 protein of a ZIKV comprising or consisting of an amino acid sequence selected from the group consisting of SEQ ID NOs: 46, 52-55, 57, 59, 60, 62, 64, 67, 69, 72, 73 and 86, 87, 89-91, or a T-cell epitope variant thereof, which differs from the original amino acid sequence of the T-cell epitope of (a), (b) or (c) by point mutation of one or more amino acid residues and which has at least 90% sequence identity or more than 95% sequence identity or 99% sequence identity with said original sequence.

As defined herein, the term “polyepitope” refers to a chimeric or recombinant molecule, in particular a chimeric or recombinant polypeptide with at least 2, in particular at least 3, preferably at least 5, and more preferably 10 or more than 10, or 15 or more than 15 T-cell epitopes identified in ZIKV proteins with the exception of full-length or native ZIKV proteins, in particular in the non-structural proteins NS1, NS3 or NS5 of ZIKV with the exception of full-length or native NS1, NS3 or NS5 proteins of ZIKV.

As defined herein, an “epitope” is a peptide or polypeptide which is an antigenic determinant, i.e. the peptide site recognized by cells of the immune system (immune cells) and especially the site necessary to elicit an immune response. The term epitope encompasses both linear epitope for which the consecutive amino acids (from 9 to 15, in particular, 8, 9, 10 or 15, more preferably 9 or 15) are recognized by immune cells and, conformational epitope for which immune cells recognize amino acids to the extent they adopt a proper configuration or conformation. Consequently, in some epitopes, the conformation (three dimensional structure) is as important as the amino acid sequence (primary structure).

As defined herein, a “T-cell epitope” is any peptide or polypeptide involved in the induction of a T cell immune response against a ZIKV, or a ZIKV and a DENV, in particular against anyone of DENV1, DENV2, DENV3, DENV4 or against multiple, in particular all DENV serotypes. In particular, said T-cell epitopes are recognized in association with class I MHC (Major Histocompatibility Complex) molecules, such as epitopes which target cells are CD8+ T lymphocytes or T epitopes recognized in association with class II MHC molecules, such as those which target cells are CD4+ T lymphocytes.

As defined herein, the term “variant thereof” refers to a T-cell epitope which differs from the original amino acid sequence of the T-cell epitope of (a), (b) or (c) by point mutation of one or more amino acid residues, in particular by 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 amino acid residues, and which has at least 90% sequence identity or more than 95% sequence identity or 99% sequence identity with said original sequence. The mutation(s) defining the variant of the T-cell epitope can be deletion(s), including especially point deletion(s) of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more amino acid residue(s) or can be substitution(s), especially conservative substitution(s) of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more amino acid residue(s). Said variant of the T-cell epitope can have an amino acid sequence which has the same length as the original amino acid sequence of the T-cell epitope of (a), (b) or (c).

As defined herein, the term “chimeric polyepitope” means any polyepitopic polypeptide comprising sub-portions or fragments of different ZIKV proteins, in particular different ZIKV NS proteins, preferably different ZIKV NS proteins selected among NS1, NS3 and NS5 proteins. Said chimeric polyepitope does not comprise full-length or native ZIKV proteins, in particular does not comprise full-length or native ZIKV NS proteins, preferably does not comprise full-length or native ZIKV NS proteins selected among NS1, NS3 and NS5 proteins.

In a particular embodiment of the invention, the chimeric polyepitope comprises less than 30 ZIKV T-cell epitopes, in particular less than 25 ZIKV T-cell epitopes, preferably less than 20 ZIKV T-cell epitopes.

In a particular embodiment of the invention, the amino acid sequences of the T-cell epitopes of a ZIKV protein taken as a whole are different from the amino acid sequences of any other epitopes of another ZIKV protein, in particular any other ZIKV T-cell epitopes of another ZIKV protein.

In another particular embodiment of the invention, the amino acid sequences of the ZIKV T-cell epitopes may differ by one or more amino acids from the amino acid sequences of other epitopes, in particular other ZIKV T-cell epitopes, and/or may have overlapping sequences, and accordingly share some amino acids.

The chimeric polyepitope of the invention comprises at least T-cell epitopes of the NS1 and NS3 proteins of a ZIKV, or at least T-cell epitopes of the NS1 and NS5 proteins of a ZIKV, or at least T-cell epitopes of the NS3 and NS5 proteins of a ZIKV, with the exception of full-length or native ZIKV proteins. Preferably, the chimeric polyepitope of the invention consists of T-cell epitopes of the NS1 and NS3 proteins of a ZIKV, or T-cell epitopes of the NS1 and NS5 proteins of a ZIKV, or T-cell epitopes of the NS3 and NS5 proteins of a ZIKV, with the exception of full-length or native ZIKV proteins.

In a preferred embodiment of the invention, the chimeric polyepitope comprises at least T-cell epitopes of the NS1, NS3 and NS5 proteins of a ZIKV, with the exception of full-length or native ZIKV proteins.

In another preferred embodiment of the invention, the chimeric polyepitope consists of T-cell epitopes of the NS1, NS3 and NS5 proteins of a ZIKV, with the exception of full-length or native ZIKV proteins.

In a particular embodiment of the invention, the chimeric polyepitope comprises sub-portions or fragments of different polyepitopes from the same ZIKV protein, in particular a NS protein of a ZIKV, preferably a NS1, NS3 or NS5 protein of a ZIKV, or even from the same polyepitopes from different ZIKV proteins, in particular NS proteins of a ZIKV, preferably NS1, NS3 and NS5 proteins of a ZIKV. The polyepitope of the invention includes the polyepitope variant. Accordingly each definition or embodiment disclosed herein applies to the variant polyepitope unless it is technically irrelevant.

As defined herein, the term “fragment” refers to a part or a portion of a ZIKV protein, preferably of a NS protein (i.e. NS1, NS3 or NS5 protein) of a ZIKV, which is shorter in length than the protein, preferably the NS protein (i.e. NS1, NS3 or NS5 protein), from which it originates. Each fragment can comprise a plurality of epitopes suitable for elicitation of an immune response, especially an immune T-cell response against a ZIKV infection or against ZIKV and DENV infections. Each fragment corresponds to a sequence of consecutive amino acids.

In a preferred embodiment of the invention, the chimeric polyepitope comprises at least the T-cell epitopes of (a), (b) and (c) as defined above, or the T-cell epitope variant thereof.

In another preferred embodiment of the invention, the chimeric polyepitope consists of (i) the T-cell epitopes of (a) and (b) as defined above, or (ii) the T-cell epitopes of (a) and (c) as defined above, or (iii) the T-cell epitopes of (b) and (c) as defined above, or (iv) the T-cell epitopes of (a), (b) and (c) as defined above, or the T-cell epitope variant thereof.

In another preferred embodiment of the invention, the T-cell epitope of (a) comprises or consists of the amino acid sequence selected from the group consisting of SEQ ID NOs: 17, 23 and 78-83, the T-cell epitope of (b) comprises or consists of the amino acid sequence selected from the group consisting of SEQ ID NOs: 31, 33, 84 and 85, and the T-cell epitope of (c) comprises or consists of the amino acid sequence selected from the group consisting of SEQ ID NOs: 46, 48, 52, 57, 62, 64, 67 and 86-91, preferably of SEQ ID NOs: 46, 52, 57, 62, 64, 67, 86, 87 and 89-91. Each of said T-cell epitope sequences contains 15 amino acid residues, i.e. is a 15-mer epitope that induces individually and/or collectively a T cell immune response. Each of these 15-mer epitopes includes individually and/or collectively at least a 9-mer epitope that also induces a T cell immune response. For example, the sequence of the 15-mer epitope in the NS1 protein of ZIKV (NS1163-177) of SEQ ID NO: 17 (FHTSVWLKVREDYSL) includes the sequence of the 9-mer epitope of SEQ ID NO: 18 (VWLKVREDY) and the sequence of the 9-mer epitope of SEQ ID NO: 19 (WLKVREDYS). This suggests that the above-mentioned 15-mer epitopes comprise at least a 9-mer epitope but can also comprise other epitopes of 9-mer or more.

In another preferred embodiment of the invention, the T-cell epitope of (a) comprises or consists of the amino acid sequence of SEQ ID NOs: 11, 12, 17-19, 23, 24, 78, 80 and 83, the T-cell epitope of (b) comprises or consists of the amino acid sequence of SEQ ID NOs: 28, 31, 33, 34, 84 and 85, and the T-cell epitope of (c) comprises or consists of the amino acid sequence of SEQ ID NOs: 48-50, 52-55, 57, 58, 60, 62, 67, 88, 89 and 90, preferably of SEQ ID NOs: 52-55, 57, 60, 62, 67, 89 and 90.

In another particular embodiment of the invention, the chimeric polyepitope further comprises at least one T-cell epitope of a ZIKV protein selected from the group consisting of:

(i) a T-cell epitope of the capsid (C) protein of a ZIKV comprising or consisting of an amino acid sequence selected from the group consisting of SEQ ID NOs: 1, 2, 4-6 and 75, (ii) a T-cell epitope of the E protein of a ZIKV comprising or consisting of an amino acid sequence selected from the group consisting of SEQ ID NOs: 7, 76 and 77, (iii) a T-cell epitope of the NS2B protein of a ZIKV comprising or consisting of the amino acid sequence of SEQ ID NO: 25, (iv) a T-cell epitope of the NS4A protein of a ZIKV comprising or consisting of the amino acid sequence of SEQ ID NO: 36, and (v) a T-cell epitope of the NS4B protein of a ZIKV comprising or consisting of the amino acid sequence selected from the group consisting of SEQ ID NOs: 40-43.

In a preferred embodiment of the invention, the chimeric polyepitope comprises T-cell epitopes of at least 2, preferably at least 3 or 4, more preferably at least 5, 6, 7, 8, 9, 10 or 11 different ZIKV proteins.

In another preferred embodiment of the invention, the chimeric polyepitope further comprises a T-cell epitope of the C protein of a ZIKV comprising or consisting of an amino acid sequence selected from the group consisting of SEQ ID NOs: 1, 2, 4-6 and 75, and a T-cell epitope of the NS4B protein of a ZIKV comprising or consisting of the amino acid sequence selected from the group consisting of SEQ ID NOs: 40-43.

Thus, the chimeric polyepitope comprises at least T-cell epitopes of the C, NS1, NS3, NS4B and NS5 proteins of a ZIKV, with the exception of said full-length or native ZIKV proteins. In particular, the chimeric polyepitope comprises at least the following T-cell epitopes:

(i) a T-cell epitope of the C protein of a ZIKV comprising or consisting of an amino acid sequence selected from the group consisting of SEQ ID NOs: 1, 2, 4-6 and 75, preferably of SEQ ID NOs: 1, 4 and 75, (ii) a T-cell epitope of the NS1 protein of a ZIKV comprising or consisting of an amino acid sequence selected from the group consisting of SEQ ID NOs: 10-12, 14, 15, 17-19, 23, 24 and 78-83, preferably of SEQ ID NOs: 17, 23 and 78-83, (iii) a T-cell epitope of the NS3 protein of a ZIKV comprising or consisting of an amino acid sequence selected from the group consisting of SEQ ID NOs: 28, 29, 31, 33-35, 84 and 85, preferably of SEQ ID NOs: 28, 31, 33-35, 84 and 85, more preferably of SEQ ID NOs: 31, 33, 84 and 85, (iv) a T-cell epitope of the NS4B protein of a ZIKV comprising or consisting of an amino acid sequence selected from the group consisting of SEQ ID NOs: 40-43, (v) a T-cell epitope of the NS5 protein of a ZIKV comprising or consisting of an amino acid sequence selected from the group consisting of SEQ ID NOs: 46, 48-50, 52-55, 57-60, 62, 64, 67, 69, 72, 73 and 86-91, preferably of SEQ ID NOs: 46, 52-55, 57, 59, 60, 62, 64, 67, 69, 72, 73 and 86, 87 and 89-91, or comprising or consisting of an amino acid sequence selected from the group consisting of SEQ ID NOs: 46, 48, 52, 57, 62, 64, 67 and 86-91, preferably of SEQ ID NOs: 46, 52, 57, 62, 64, 67, 86, 87 and 89-91, or a T-cell epitope variant thereof, which differs from the original amino acid sequence of the T-cell epitope of (i), (ii), (iii), (iv) or (v) by point mutation of one or more amino acid residues and which has at least 90% sequence identity or more than 95% sequence identity or 99% sequence identity with said original sequence.

In another preferred embodiment of the invention, in the above-mentioned chimeric polyepitope:

(i) the T-cell epitope of the C protein of a ZIKV comprises or consists of the amino acid sequence of SEQ ID NOs: 4, 5, 6 and 75, (ii) the T-cell epitope of the NS1 protein of a ZIKV comprises or consists of the amino acid sequence of SEQ ID NOs: 11, 12, 17-19, 23, 24, 78, 80 and 83, (iii) the T-cell epitope of the NS3 protein of a ZIKV comprises or consists of the amino acid sequence of SEQ ID NOs: 28, 31, 33, 34, 84 and 85, (iv) the T-cell epitope of the NS4B protein of a ZIKV comprises or consists of the amino acid sequence of SEQ ID NOs: 40 and 41, and (v) the T-cell epitope of the NS5 protein of a ZIKV comprises or consists of the amino acid sequence of SEQ ID NOs: 48-50, 52-55, 57, 58, 60, 62, 67, 88, 89 and 90, preferably of SEQ ID NOs: 52-55, 57, 60, 62, 67, 89 and 90.

In another preferred embodiment of the invention, the chimeric polyepitope consists of T-cell epitopes of the C, NS1, NS3, NS4B and NS5 proteins of a ZIKV, with the exception of full-length or native ZIKV proteins.

All the definitions directed to the NS1, NS3 and NS5 proteins of a ZIKV mentioned above also apply to other proteins of a ZIKV, in particular to the C, E, NS1, NS2B, NS3, NS4A, NS4B and NS5 proteins of a ZIKV.

In a preferred embodiment of the invention, the chimeric polyepitope is (i) for use in the prevention of a ZIKV infection in a human subject or (ii) for use in the prevention of ZIKV and Dengue virus (DENV) infections in a human subject.

As defined herein, the term “prevention” refers to primary, secondary and tertiary preventions. Prevention of a ZIKV infection or ZIKV and DENV infections means that said infection(s) and associated risk factors are minimized, i.e. are obstructed or delayed. In particular, said infection(s) may be prevented before it occurs or identified at an early stage so that the symptoms of said infection(s) may be reduced.

In a more preferred embodiment of the invention, when the polyepitope is used in the prevention of a ZIKV infection in a human subject, the T-cell epitopes are ZIKV-specific epitopes comprising or consisting of an amino acid sequence selected from the group consisting of SEQ ID NOs: 1, 2, 5, 10, 11, 19, 27, 31, 40-43, 46, 72, 73, 75, 78-80, 82, 84, 85, 87 and 91.

In another more preferred embodiment of the invention, when the polyepitope is used in the prevention of ZIKV and DENV infections in a human subject, the T-cell epitopes are ZIKV-DENV cross-reactive epitopes comprising or consisting of an amino acid sequence selected from the group consisting of SEQ ID NOs: 1, 5, 6, 12, 14, 15, 17-19, 23, 24, 27, 28, 33-35, 40, 41, 46, 48-50, 52-55, 57, 59, 60, 62, 64, 67, 69, 72, 73, 84, 85 and 86-91, preferably of SEQ ID NOs: 1, 5, 6, 12, 14, 15, 17-19, 23, 24, 27, 28, 33-35, 40, 41, 46, 52-55, 57, 59, 60, 62, 64, 67, 69, 72, 73, 84, 85, 86, 87 and 89-91.

To be noted that T-cell epitopes comprising or consisting of an amino acid sequence selected from the group consisting of SEQ ID NOs: 1, 5, 19, 27, 40, 41, 46, 72, 73, 84, 85, 87 and 91 are both capable of inducing a T cell immune response in ZIKV donors and in DENV/ZIKV donors.

A non-exhaustive list of ZIKV T-cell epitopes, in particular ZIKV-specific T-cell epitopes and/or ZIKV-DENV cross-reactive T-cell epitopes, is provided in Tables 2 and 3 below. Said ZIKV T-cell epitopes comprise amino acid sequences defined as SEQ ID NOs: 1-91.

In a particular embodiment of the invention, the chimeric polyepitope comprises human leukocyte antigen (HLA)-restricted epitopes. The expression “HLA-restricted” refers to the capacity for a particular epitope to have an affinity for this type of HLA molecule. The HLA molecules used in the invention encompass either class I molecules (designated HLA-A, B or C) or class II molecules (designated DRB).

In another particular embodiment of the invention, the chimeric polyepitope elicits a human leukocyte antigen (HLA)-restricted CD8⁺ and/or CD4⁺ T cell response (i) against ZIKV, or (ii) against ZIKV and DENV, in particular DENV serotype 1 (DENV1), DENV serotype 2 (DENV2), DENV serotype 3 (DENV3) and DENV serotype 4 (DENV4), preferably against DENV serotype 1 (DENV1).

Complete nucleotide sequences of the reference genomes of the 4 dengue virus serotypes can be accessed from the Genbank database under accession numbers NC_001477.1, NC_001474.2, NC_001475.2 and NC_002640.1 respectively.

In a particular embodiment of the invention, said DENV is from the following strains: GenBank KDH0026A (DENV1), GenBank R0712259 (DENV2), GenBank KDH0010A (DENV3) and GenBank CRBIP10.4VIMFH4 (DENV4).

In a particular embodiment of the invention, the polyepitope elicits antigenic responses with HLA restriction such as HLA-A*0201, HLA-A*2402, HLA-B*0702, HLA-B*3501, HLA-B*4002, preferably HLA-A*0201, HLA-A*2402, HLA-B*0702 and HLA-B*3501.

In a particular embodiment of the invention, (i) at least T-cell epitopes of the NS1 and NS3 proteins of a ZIKV, or (ii) at least T-cell epitopes of the NS1 and NS5 proteins of a ZIKV, or (iii) at least T-cell epitopes of the NS3 and NS5 proteins of a ZIKV, or (iv) at least T-cell epitopes of the NS1, NS3 and NS5 proteins of a ZIKV, or (v) at least T-cell epitopes of the C, NS1, NS3, NS4B and NS5 proteins of a ZIKV, with the exception of full-length or native ZIKV proteins, are assembled in a unique polypeptide, preferably in a fusion polypeptide. Preferably, the above-defined T-cell epitopes are assembled in a fusion polypeptide.

Said T-cell epitopes can be directly or indirectly fused to each other.

According to a particular embodiment of the invention, one T-cell epitope is fused “directly” with another T-cell epitope, i.e. the 3′ end of the T-cell epitope is directly linked to the 5′ end of the second T-cell epitope (and so on), corresponding to a chimeric polyepitope composed of consecutive T-cell epitopes from at least two different ZIKV proteins, in particular the ZIKV C protein and the ZIKV NS proteins chosen among NS1, NS3, NS4B and NS5, in particular originating from a consensus sequence of ZIKV. According to an alternative embodiment, the fusion of the at least two T-cell epitopes, in particular the at least three T-cell epitopes, is “indirect” and accordingly involves the presence of other, in particular non-NS, amino acid residues segment(s), in particular comprising from 1 to 15 amino acid residues, which do not form human T-cell epitopes.

The chimeric polyepitope of the invention comprises or consists of one or more antigenic regions, in particular between 2 and 15 antigenic regions, preferably between 10 and 15 antigenic regions, more preferably 11, 12, 13 or 14 antigenic regions.

As defined herein, the term “antigenic region” refers to a region comprising one or more ZIKV T-cell epitopes, i.e. a group of ZIKV T-cell epitopes. The amino acid sequences of said ZIKV T-cell epitopes may differ by one or more amino acid residues from the amino acid sequences of other ZIKV T-cell epitopes, and/or may have overlapping sequences, and accordingly share some amino acids. In a determined antigenic region, said ZIKV T-cell epitopes are of the same ZIKV protein, in particular are of the C, NS1, NS3, NS4B and NS5 proteins of the ZIKV, preferably are of the NS1, NS3, and NS5 proteins of the ZIKV. The chimeric polyepitope of the invention may comprise one or more different antigenic regions of the same ZIKV protein.

In a particular embodiment of the invention, it is necessary to check that the adjacent amino acid sequences located on both sides of the junction between 2 contiguous antigenic regions do not form new epitopes, in particular new strong human T-cell epitopes. As a consequence, said amino acid sequences consist of no more than 15 amino acid residues and are selected on the basis of the their low binding prediction to the HLA-A*01:01, HLA-A*02:01, HLA-A*03:01, HLA-A*11:01, HLA-A*24:02, HLA-B*07:02, HLA-B*35:01 and HLA-B*40:03, alleles, according to the Immuno Epitope Database (IEDB) analysis resource (http://tools.immuneepitope.org/mhci/). For example, in the fusion between two ZIKV protein fragments, in particular between two ZIKV protein fragments selected from the group consisting of the C, NS1, NS3, NS4B and NS5 proteins of a ZIKV, or between or two antigenic regions, the region surrounding the fusion junction comprises a peptide sequence consisting of no more than 15 amino acid residues and which does not form a strong epitope. Thus the junctional peptide may comprise 14 amino acid residues of a first ZIKV protein and 1 amino acid residue of a second ZIKV protein, or 13 amino acid residues of a first ZIKV protein and 2 amino acid residues of a second ZIKV protein, or 12 amino acid residues of a first ZIKV protein and 3 amino acid residues of a second ZIKV protein, or 11 amino acid residues of a first ZIKV protein and 4 amino acid residues of a second ZIKV protein, or 10 amino acid residues of a first ZIKV protein and 5 amino acid residues of a second ZIKV protein, or 9 amino acid residues of a first ZIKV protein and 6 amino acid residues of a second ZIKV protein, or 8 amino acid residues of a first ZIKV protein and 7 amino acid residues of a second ZIKV protein, or 7 amino acid residues of a first ZIKV protein and 8 amino acid residues of a second ZIKV protein, or 6 amino acid residues of a first ZIKV protein and 9 amino acid residues of a second ZIKV protein, or 5 amino acid residues of a first ZIKV protein and 10 amino acid residues of a second ZIKV protein, or 4 amino acid residues of a first ZIKV protein and 11 amino acid residues of a second ZIKV protein, or 3 amino acid residues of a first ZIKV protein and 12 amino acid residues of a second ZIKV protein, or 2 amino acid residues of a first ZIKV protein and 13 amino acid residues of a second ZIKV protein, or 1 amino acid residue of a first ZIKV protein and 14 amino acid residues of a second ZIKV protein. Said first and second ZIKV proteins may be different or identical.

In a particular embodiment of the invention, the chimeric polyepitope has less than 1500 amino acid residues, in particular less than 1000 amino acid residues.

An example of a chimeric polyepitope that can be used in the present invention has an amino acid sequence of SEQ ID NO: 99 consisting of 962 amino acid residues. Said chimeric polyepitope consists of 11 antigenic regions, wherein the first antigenic region is located from amino acid residues 1 to 93 (SEQ ID NO: 102), the second antigenic region is located from amino acid residues 94 to 206 (SEQ ID NO: 104), the third antigenic region is located from amino acid residues 207 to 270 (SEQ ID NO: 106), the fourth antigenic region is located from amino acid residues 271 to 286 (SEQ ID NO: 108), the fifth antigenic region is located from amino acid residues 287 to 331 (SEQ ID NO: 110), the sixth antigenic region is located from amino acid residues 332 to 473 (SEQ ID NO: 112), the seventh antigenic region is located from amino acid residues 474 to 547 (SEQ ID NO: 114), the eighth antigenic region is located from amino acid residues 548 to 766 (SEQ ID NO: 116), the ninth antigenic region is located from amino acid residues 767 to 821 (SEQ ID NO: 118), the tenth antigenic region is located from amino acid residues 822 to 839 (SEQ ID NO: 120) and the eleventh antigenic region is located from amino acid residues 840 to 962 (SEQ ID NO: 122).

The native and optimized sequences of the polynucleotide encoding said chimeric polyepitope are as defined in SEQ ID NOs: 100 and 101 respectively.

Another nucleotide sequence of the polynucleotide encoding said chimeric polyepitope is as defined in SEQ ID NO: 124.

The first antigenic region of said chimeric polyepitope comprises T-cell epitopes of the C protein of ZIKV. The native sequence of the polynucleotide encoding said first antigenic region is as defined in SEQ ID NO: 103.

The second antigenic region of said chimeric polyepitope comprises T-cell epitopes of the NS1 protein of ZIKV. The native sequence of the polynucleotide encoding said second antigenic region is as defined in SEQ ID NO: 105.

The third antigenic region of said chimeric polyepitope comprises T-cell epitopes of the NS1 protein of ZIKV. The native sequence of the polynucleotide encoding said third antigenic region is as defined in SEQ ID NO: 107.

The fourth antigenic region of said chimeric polyepitope comprises T-cell epitopes of the NS1 protein of ZIKV. The native sequence of the polynucleotide encoding said fourth antigenic region is as defined in SEQ ID NO: 109.

The fifth antigenic region of said chimeric polyepitope comprises T-cell epitopes of the NS3 protein of ZIKV. The native sequence of the polynucleotide encoding said fifth antigenic region is as defined in SEQ ID NO: 111.

The sixth antigenic region of said chimeric polyepitope comprises T-cell epitopes of the NS3 protein of ZIKV. The native sequence of the polynucleotide encoding said sixth antigenic region is as defined in SEQ ID NO: 113.

The seventh antigenic region of said chimeric polyepitope comprises T-cell epitopes of the NS4B protein of ZIKV. The native sequence of the polynucleotide encoding said seventh antigenic region is as defined in SEQ ID NO: 115.

The eighth antigenic region of said chimeric polyepitope comprises T-cell epitopes of the NS5 protein of ZIKV. The native sequence of the polynucleotide encoding said eighth antigenic region is as defined in SEQ ID NO: 117.

The ninth antigenic region of said chimeric polyepitope comprises T-cell epitopes of the NS5 protein of ZIKV. The native sequence of the polynucleotide encoding said ninth antigenic region is as defined in SEQ ID NO: 119.

The tenth antigenic region of said chimeric polyepitope comprises T-cell epitopes of the NS5 protein of ZIKV. The native sequence of the polynucleotide encoding said tenth antigenic region is as defined in SEQ ID NO: 121.

The eleventh antigenic region of said chimeric polyepitope comprises T-cell epitopes of the NS5 protein of ZIKV. The native sequence of the polynucleotide encoding said tenth antigenic region is as defined in SEQ ID NO: 123.

The present invention also relates to an association of the chimeric polyepitope of the invention, with a distinct immunogenic polypeptide comprising other ZIKV antigens. Said association of polypeptides may be achieved as a result of expression of the polynucleotides encoding each of said chimeric polyepitope and distinct immunogenic polypeptide, from a vector as disclosed herein. Alternatively, said association may result from an amino acid construct encompassing said chimeric polyepitope and distinct immunogenic polypeptide.

The chimeric polyepitope of the invention can be synthesized chemically, or produced either in vitro (cell free system) or in vivo after expression of the nucleic acid molecule encoding the chimeric polyepitope in a cell system.

To check the correct expression of the chimeric polyepitope of the invention in an in vitro cell system, said chimeric polyepitope may comprise a tag sequence in its 3′ end.

In the present invention, the ZIKV protein, in particular the C, NS1, NS3, NS4B or NS5 protein of ZIKV, preferably the NS1, NS3 or NS5 protein of ZIKV, is in particular an antigen designed using a consensus sequence for the ZIKV. In particular, said antigen is designed using the consensus amino acid sequence of Zika viruses as observed circulating from 2013 and onward.

In a particular embodiment of the invention, said ZIKV is from the African lineage, in particular from the African strain ArD158084 (GenBank: KF383119) or African strain ArD128000 (GenBank: KF383117), or African isolate ARB13565 (GenBank: KF268948), or from the Asian lineage, in particular from the Asian strain FLR (GenBank: KX087102), or Asian isolate SSABR1 (GenBank: KU707826), or Asian isolate Z1106031 (GenBank: KU312314), or Asian isolate Bahia07 (GenBank: KU940228), or Asian strain FVM00318/VEN/Maracay/2016 (GenBank: KY693680), or Asian isolate FLR (GenBank: KU820897).

In another particular embodiment of the invention, said ZIKV corresponds to various lineages of ZIK viruses including strains that circulated in the Pacific and Americas since 2013.

In a preferred embodiment of the invention, the C, NS1, NS3, NS4B or NS5 protein of the ZIKV has an amino acid sequence which is a consensus amino acid sequence representative of the C, NS1, NS3, NS4B or NS5 sequences of a selection of various strains of ZIKV including from the Asian lineage, in particular is from the ZIKV strains (GenBank: KX087102, KU707826, KU312314, KU940228, KY693680, KU820897).

The invention also relates to an isolated or purified polynucleotide encoding the chimeric polyepitope according to the invention.

The invention also relates to an isolated or purified polynucleotide encoding the chimeric polyepitope according to the invention, in a nucleic acid construct further comprising a polynucleotide encoding other ZIKV antigens.

As defined herein, the term “isolated or purified” means molecules which have been altered by man from their native state, i.e. if the molecules exist in nature, they have been changed and/or withdrawn from their initial environment. As an example, a polynucleotide naturally present and found in the biological environment of a living organism which naturally expresses it is not “isolated” in this context. However, the same polynucleotide when separated from its natural environment and/or obtained by cloning, amplification and/or chemical synthesis is considered in the present invention to be “isolated”. Further, a polynucleotide which is introduced into an organism by transformation, gene manipulation or any other recombination method is “isolated” even if it is present in said organism.

As defined herein, the term “encoding” defines the ability of the nucleic acid molecules to be transcribed and where appropriate translated for product expression into selected cells or cell lines, when said molecule is placed under expression control sequences including promoter for transcription. Accordingly a “polynucleotide encoding” according to the invention is either limited to the nucleic acid having the sequence translated into the amino acid sequence or alternatively when specified comprises also the expression control sequences.

The present invention also relates to a vector, in particular a non-replicating vector, suitable for the delivery of the chimeric polyepitope according to the invention, wherein said vector is a recombinant molecule carrying the polyepitope, or is a viral vector expressing the polyepitope, or a mammalian expression vector expressing the polyepitope such as the pcDNA3 vector, the pcDNA5 vector, the pcDNA6 vector, the pCI vector and the pCMV vector.

The present invention also relates to a vector comprising the polynucleotide according to the invention.

As defined herein, the term “vector” refers to a polynucleotide construct designed for transduction/transfection of one or more cell types. Vectors may be, for example, “cloning vectors” which are designed for isolation, propagation and replication of inserted polynucleotides (designated as the insert), “expression vectors” which are designed for expression of a polynucleotide molecule especially for expression of the insert in a host cell, or a “viral vector” which is designed to result in the production of recombinant virus particles or virus-like particles, or “shuttle vectors”, which comprise the attributes of more than one type of vector.

A number of vectors suitable for transduction or for transfection of cells, in particular for stable transfection of cells and bacteria are available to the public (e.g. plasmids, viruses), as are methods for constructing such cell lines. It will be understood that the present invention encompasses any type of vector comprising any of the polynucleotides of the invention.

In a particular embodiment of the invention, the present invention relates to an expression vector, which may be a plasmid comprising as polynucleotide insert(s), one or a plurality of the nucleic acid molecules defined herein. In a particular embodiment, the plasmid comprises as an insert a polynucleotide encoding the chimeric polyepitope of the invention as defined herein and optionally comprises the polynucleotide encoding other ZIKV antigens.

Vectors well known to the skilled person that can be used in the present invention encompass the measles virus vector, in particular live-attenuated measles virus vector (for example, as disclosed in Combredet, C. et al., 2003, J Virol, 77(21): 11546-11554, in the European patent application EP17305676.3 and in the international applications WO2004/000876, WO2004/001051, WO2014/049094, WO2015/197565), lentiviral vectors (for example, as disclosed in the international applications WO2005/111221, WO2007/052165, WO2008/078198, WO2009/019612 and WO2016/091836), or mRNA (for example, Moderna's mRNA Therapeutics™ platform; as disclosed in the international applications WO2012135805, WO2013039861 and WO2015/085318 or in Expert Opinion by Youn H. and Chung J K. Expert Opin Biol Ther. 2015 Sep. 2; 15(9): 1337-1348 published online 2015 Jun. 30. doi: 10.1517/14712598.2015.1057563).

The present invention also relates to a host cell transformed with the polynucleotide according to the invention or the vector according to the invention.

The host cell may be genetically transformed with the polynucleotide encoding the chimeric polyepitope of the invention and optionally with the polynucleotide encoding other ZIKV antigens. A particular host cell may thus be genetically transformed with a vector of the invention.

The host cell of the invention may be transfected with a genome vector by methods well known to the man skilled in the art, i.e. by chemical transfection (calcium phospate, lipofectamine), lipid-based techniques (liposome), electroporation, photoporation, use of viral vectors . . . .

In a particular embodiment of the invention, a cell is transformed or transduced with a polynucleotide of the invention, in a way enabling integration of the polynucleotide in the cell genome either by a recombination with the homologous cellular sequence or by insertion in the cellular genome. The transfection, infection or transduction can occur ex vivo, i.e. in an artificial environment outside the living organism.

As used herein, the terms “transfected”, “transformed” or “infected” refer to a cell comprising a vector of the invention (transient expression), whereas the term “genetically transformed” refers to a cell whose genome has been definitively modified by a polynucleotide of the invention (permanent expression).

Said transitory or stably transformed cells can be any prokaryotic (bacteria) or eukaryotic (yeast, insect or animal including mammal especially human) cells. In an embodiment, cells are non-human cells. In a particular embodiment, cells of the invention are isolated human cells, “isolated” meaning outside of their natural environment.

In a particular embodiment of the invention, the host cell is an eukaryotic cell, such as an avian cell, in particular a CEF (chick embryo fibroblast) cell, a mammalian cell, in particular HEK-293 (human embryonic kidney) cells, which cell line 293 is deposited with the ATCC under No. CRL-1573 (as disclosed in the international application WO2008/078198), or a yeast cell.

The present invention also relates to an immunogenic composition comprising at least one component selected from the group consisting of:

(i) the chimeric polyepitope according to the invention, (ii) the polynucleotide according to the invention, (iii) the vector according to the invention, and (iv) the host cell according to the invention.

In a particular embodiment of the invention, the immunogenic composition further comprises an adjuvant and/or a pharmaceutically acceptable vehicle.

In another particular embodiment of the invention, the immunogenic composition further comprises a polynucleotide encoding other ZIKV antigens.

In a particular embodiment of the invention, the immunogenic composition does not comprise an adjuvant and/or a pharmaceutically acceptable vehicle.

As defined herein, a pharmaceutically acceptable vehicle encompasses any substance that enables the formulation of the polyepitope, the polynucleotide, the vector according to the invention within a composition. A vehicle is any substance or combination of substances physiologically acceptable i.e., appropriate for its use in a composition in contact with a host, especially a human, and thus non-toxic. Examples of such vehicles are phosphate buffered saline solutions, distilled water, emulsions such as oil/water emulsions, various types of wetting agents sterile solutions and the like.

As defined herein, an adjuvant includes, for example, liposomes, oily phases, such as Freund type adjuvants, generally used in the form of an emulsion with an aqueous phase or can comprise water-insoluble inorganic salts, such as aluminium hydroxide, zinc sulphate, colloidal iron hydroxide, calcium phosphate or calcium chloride.

In another particular embodiment of the invention, the immunogenic composition is formulated for an administration through parenteral route such as subcutaneous (s.c.), intradermal (i.d.), intramuscular (i.m.), intraperitoneal (i.p.) or intravenous (i.v.) injection.

In another particular embodiment of the invention, the immunogenic composition is administered in one or multiple administration dose(s), in particular in a prime-boost administration regime.

The quantity to be administered (dosage) depends on the subject to be treated, including the condition of the patient, the state of the individual's immune system, the route of administration and the size of the host. Suitable dosages range from 10³ TCID50 to 10⁷ TCID50 for a viral vector or 100 micrograms of the plasmid DNA, and can be modified by one skilled in the art, depending on circumstances.

The present invention also relates to a vaccine composition comprising at least one component selected from the group consisting of:

(i) the chimeric polyepitope according to the invention, (ii) the polynucleotide according to the invention, (iii) the vector according to the invention, and (iv) the host cell according to the invention.

In a preferred embodiment of the invention, the immunogenic or vaccine composition is for use in the prevention of a ZIKV infection in a human subject or (ii) for use in the prevention of ZIKV and Dengue virus (DENV) infections in a human subject.

The present invention also relates to the induction of immune responses in vivo against the epitopes of the ZIKV polyepitope, in mice expressing the human HLA class I alleles: HLA-A*02:01, or HLA-A*24:02, or HLA-B*07:02 or HLA-B*35:01. The immunization of mice is performed following a prime boost administration regimen, with a first intradermal injection of plasmid DNA encoding the ZIKV polyepitope (2 simultaneous intradermal injections of 50 micrograms plasmid DNA in the lower back, followed by in vivo electroporation, using a pre-defined procedure), followed by a boost immunization 3 weeks later (2 intradermal injections of 50 micrograms plasmid DNA in the lower back, and electroporation, using the same pre-defined procedure). The electroporation settings, using the AgilePulse apparatus (BTX, Harvard apparatus) consist of 3 Voltage groups: including the first one with 450V, a pulse length of 50 microseconds, a pulse interval of 0.2 microseconds and 1 pulse, the second one with 450V, a pulse length of 50 microseconds, a pulse interval of 50 microseconds and 1 pulse, and a third one with 110V, a pulse length of 10 milliseconds, a pulse interval of 20 milliseconds and 8 pulses. Ten days after the boost immunization, the spleen of the immunized mice are taken and spleen cells are tested for their ability to secrete Interferon gamma in response to in vitro stimulation with the specific peptides derived from the ZIKV polyepitope, according to the ELISPOT assay.

Other features and advantages of the invention will be apparent from the examples which follow and will also be illustrated in the figures.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1. ZIKV-specific response magnitude and frequency of responding donors. Cumulative IFN-γ responses (as spot-forming cells (SFCs) per million cells) for each overlapping peptide spanning the ZIKV proteome is shown for (A) all donors, (B) ZIKV donors or (C) DENV/ZIKV donors. The heat map indicates the number of donors with a positive IFN-γ response to each peptide within each protein (C, capsid; M, membrane; E, envelope, NS1, NS2A, NS2B, NS3, NS4A, NS4B, and NS5). The numbers below each graph represent percentages of the total response for each protein.

FIG. 2. ZIKV donors with previous DENV infection reveal a broader T-cell response with a higher magnitude. (A) Breadth and (B) magnitude of responses in ZIKV and DENV/ZIKV donors. Each dot represents one donor (open circles, ZIKV donors; filled circles, DENV/ZIKV donors) and the bars represent the median value for each group of donors. The P values were calculated using the nonparametric two-tailed Mann-Whitney test. Frequency of responses against individual peptides, per donor, in ZIKV (C) and DENV/ZIKV (D) donors. Each dot represents one peptide. The bars represent the median response for each donor.

FIG. 3. Comparison of the magnitude of response and sequence identity with DENV in ZIKV and DENV/ZIKV donors. Each dot represents the cumulative response of different donors against one peptide. Percentages represent the mean identity value between the sequences of ZIKV and the 4 DENV serotypes. (A) peptides inducing a response in ZIKV donors. (B) peptides inducing a response in DENV/ZIKV donors.

FIG. 4. Schematic representation of the 18AAHK3C_pVAX-ZIKV_PolyEpitop_pVAX1 plasmid. The inventors used the pVAX1 plasmid commercialized by Thermo Fisher Scientific. The polynucleotide encoding a chimeric polyepitope of ZIKV as defined in SEQ ID NO: 124 was inserted in said plasmid.

FIG. 5. HLA-A*2402 transgenic mice were immunized by intradermal injections and in vivo electroporation (prime with 2×50 μg DNA at day 0, and boost with 2×50 μg DNA at day 21) with the plasmid DNA coding for a chimeric polyepitope of ZIKV. Said chimeric polyepitope of ZIKV had the amino acid sequence of SEQ ID NO: 99. The nucleotide sequence of the polynucleotide encoding said chimeric polyepitope was as defined in SEQ ID NO: 124. Fourteen days after the boost, immunized mice were transiently depleted for IFN alpha response by intraperitoneal injection with 2 mg anti-IFNAR antibody (MAR1-5A3) and virus inoculation was performed 24h after treatment with anti-IFNAR antibody. For virus inoculation, mice received intra-peritoneal injection of the French Guyana strain FG15 of ZIKV, using 10³ pfu per mouse, and viremia was quantified by qRT-PCR at days 1, 2, 3 and 6 after virus inoculation. Four mice were used as control mice (electroporation with an empty vector) and 5 mice were vaccinated with the pZIKV construct (electroporation with the plasmid DNA coding for the chimeric polyepitope of ZIKV). The electroporation settings, using the AgilePulse apparatus (BTX, Harvard apparatus) consisted of 3 Voltage groups: including the first one with 450V, a pulse length of 50 microseconds, a pulse interval of 0.2 microseconds and 1 pulse, the second one with 450V, a pulse length of 50 microseconds, a pulse interval of 50 microseconds and 1 pulse, and a third one with 110V, a pulse length of 10 milliseconds, a pulse interval of 20 milliseconds and 8 pulses.

EXAMPLES Ethics Statement

Human blood samples were obtained from healthy adult donors from the Fundación Hematológica Colombia (Bogota D.C., Colombia) in an anonymous manner. All protocols described in this study were approved by the institutional review board (IRB) of the EL Bosque University (Colombia).

Human Blood Samples

Donors were of both sexes and between 20 and 60 years of age. A total of 82 samples were obtained from different ZIKV-endemic areas near Bogota D.C. (mainly from Villavicencio, Meta) over a time course of three months between October and December 2016. PBMCs were purified by density gradient centrifugation (Lymphoprep™; Stemcell technologies) and resuspended in FBS (Gibco) containing 10% dimethyl sulfoxide and cryopreserved in liquid nitrogen. Eleven of the 82 blood samples obtained had to be excluded from the study due to poor viability of cells.

Viruses and Cell Lines The in vitro assays were conducted using the DENV1 KDH0026A (provided by Dr L. Lambrecht, Institut Pasteur, Paris), DENV2 R0712259 (provided by Dr. A. Failloux, Institut Pasteur, Paris), DENV3 KDH0010A (provided by Dr. L. Lambrecht, Institut Pasteur, Paris), DENV4 CRBIP10.4VIMFH4 (from the Institut Pasteur Collection) and ZIKV KU312312 (provided by Dr. Dominique Rousset, Institut Pasteur. Cayenne). All viruses were grown using the Aedes Albopictus mosquito cell line C6/36 cultured in Leibovitz's L-15 medium supplemented with 10% fetal bovine serum containing 0.1 mM non-essential amino acids and 1× tryptose phosphate broth. Vero-E6 cells and DC-SIGN-expressing U937 were kindly provided by Dr M. Flamand and Dr B. Jacquelin (Institut Pasteur, Paris), respectively.

HLA Typing

Genomic DNA isolated from PBMCs of the study subjects by standard techniques (QIAmp; Qiagen) was used for HLA typing. High resolution Luminex-based typing for HLA class I (alleles A, B and C) and HLA class II (allele DRB1) was used according to the manufacturer's protocol (Sequence-Specific Oligonucleotides (SSO) typing; Immucor, Lifecodes).

Serology

ZIKV seropositivity was determined using a recombinant antigen-based (EDIII antigen) indirect ELISA, as previously described (Aubry M, et al. 2017, Emerging infectious diseases 23(4):669-672). Briefly, 96-well plates (Nunc, Life Technologies, Rochester, N.Y.) were coated overnight at 4° C. with 50 ng of antigen in PBS. After washing, 200 μl PBS containing 3% skimmed milk and 0.1% Tween-20 were added for 1 hr at 37°. The blocking solution was replaced by 100 μl of plasma diluted 1:500 in PBS containing 1.5% BSA and 0.1% Tween-20, and plates were incubated at 37° C. for 60 min. After three washes, bound antibodies were detected with a horseradish peroxidase-conjugated goat anti-human IgG immunoglobulin (ROCKLAND). Following incubation at 37° C. for 1 hr and three washes, 100 μl of a substrate solution containing TMB (KPL, Eurobio) were added. After 15 min incubation, the optical density (OD) was determined at 650 nm with an automated plate reader (Tecan infinite 200 pro). Each plasma sample was tested in duplicate. Plasma samples obtained from individuals with positive DENV IgG serology collected before the ZIKV outbreak were used as negative controls. The cut-off was calculated from the negative controls and was 0.196. DENV seropositivity was determined by indirect ELISA for IgGs (Panbio; Alere) and by capture ELISA for IgM (Tecnosuma) following the manufacturer's instructions. For further characterization of seropositive donors, and to confirm the specificity of the ELISA, a flow cytometry-based neutralization assay was performed as described previously (Andreatta M, et al. 2015, Immunogenetics 67(11-12):641-650; Nielsen M & Andreatta M 2016, Genome Med 8(1):33). Briefly, 10-fold serial dilutions of plasma samples were incubated at 37° C. for 1 hour with a dilution of virus inducing 7-15% infection. Virus-antibody mixture was then added to U937-DC-SIGN cells for neutralization of DENV1-4 infection, or to Vero cells for neutralization of ZIKV infection, for 2 hours at 37° C. after which cells were washed 2 times with fresh medium and then incubated for 24h. The cells were then fixed with 4% paraformaldehyde, stained with 4G2 antibody conjugated to Alexa-488, and the percentage of infected cells was measured by flow cytometry. The neutralization titer of antibodies was expressed as the reciprocal dilution of plasma at which 50% of the virus was inhibited. Plasma samples from donors collected before ZIKV outbreak or from negative samples provided from the Kits to detect anti-DENV antibodies did not reveal any neutralization activity against ZIKV or DENV infection, respectively. Following the ELISA and neutralization assays, from the 71 plasma samples selected for this study, a total of nine samples from ZIKV-seropositive individuals and eleven samples from DENV/ZIKV-seropositive individuals were further selected for ELISPOT analysis. The full list of the twenty blood donors included in this study is listed in Table 1.

Viral Sequences

The identical amino acid sequence of ZIKV from Colombia (GenBank KX087102 and KU820897) was used as a reference for the set of overlapping 15-mer peptides.

A total of 50 full length protein coding DENV sequences from Colombia (serotype 1: 14 sequences; serotype 2: 16 sequences; serotype 3: 13 sequences; serotype 4: 7 sequences) were retrieved from GenBank and used for pairwise sequence identity comparisons.

Peptides

All peptides were synthesized by Mimotopes (Victoria, Australia). A total of 853 15-mer peptides overlapping by 11 amino acids and 197 9-mer peptides overlapping by eight amino acids were tested by ELISPOT assay. For the identification of T-cell epitopes, 15-mer peptides were combined into pools of 12 peptides, and individual peptides from the positive pools were tested in a second ELISPOT assay. Following the identification of the positive 15-mer peptides, and according to their HLA class I or class II restriction potential (predicted or shared between at least two donors), 9-mer peptides were synthesized and tested individually.

Ex Vivo IFN-γ ELISPOT Assay

PBMCs (2×10⁵) were incubated in 96-well flat bottom plates (MSIPS 4510, Millipore, Bedford, Mass.) coated with anti-IFN-γ mAb (clone 1-D1K, Mabtech, Sweden) with 0.2 ml of complete RPMI containing 10% human AB serum with pools of 12 peptides (2 μg/ml, final concentration) or individual peptides (1 μg/ml, final concentration) for 20 hours. Following a 20h-incubation at 37° C., the wells were washed with PBS/0.05% Tween 20 and then incubated with biotinylated anti-IFN-γ mAb (clone 7-B6-1, Mabtech) for 1h 30 mn. The spots were developed using Streptavidin-alkaline phosphatase (Mabtech) and BCIP/NBT substrate (Promega, France) and counted using an automated ELISPOT reader (Immunospot, Cellular Technology Limited, Germany). The number of IFN-γ-producing cells was expressed as spot forming cells (SFC) relative to 1×10⁶ PBMCs. Values were calculated by subtracting the number of spots detected in the non-stimulated control wells. Values were considered positive if they were equal to or greater than 20 spots and at least three times above the means of the unstimulated control wells. As a positive control, cells were stimulated with CEF peptide pool (Mabtech).

Immunogenicity and HLA Restrictions Prediction

The evaluation of binding possibilities of peptides to MHC class I and class II alleles was analyzed using the NetMHCpan3.0 and NetMHCIIpan3.1 servers, respectively (Andreatta M, et al. 2015, Immunogenetics 67(11-12):641-650; Nielsen M & Andreatta M 2016, Genome Med 8(1):33).

Statistics

All data were analyzed with Prism software version 7.0 (GraphPad Software). Statistical significance was determined using the nonparametric two-tailed Mann-Whitney test to compare two independent groups. Differences were considered significant at P<0.05.

Results Identification of Immunodominant Regions of the ZIKV Proteome

To investigate T-cell immunity induced after ZIKV infection, the inventors examined responses from blood donors living in a ZIKV endemic area in gamma interferon (IFN-γ)-specific enzyme-linked immunosorbent spot (ELISPOT) assays. Blood samples from all study participants were tested for the presence of ZIKV IgG and DENV IgM and IgG by ELISA, and for the presence of virus-specific antibodies by flow cytometry-based neutralization assay against ZIKV and the 4 DENV serotypes, and PBMCs from ZIKV-seropositive individuals were HLA-typed. Details of the blood donors included in this study are listed in Table 1. PBMCs from 20 ZIKV-seropositive donors were screened for T-cell reactivity against pools of 15-mer peptides (overlapping by 11 amino acids) spanning the entire ZIKV proteome. Analysis of the response magnitude (as spot forming cells (SFC) per 10⁶ cells) and frequency of responding donors revealed that the non-structural (NS) proteins NS1, NS3 and NS5 were the most vigorously and frequently recognized proteins, and accounted for 69% of the total response (FIG. 1A). Strikingly, these NS1, NS3 and NS5 proteins represented 15%, 19% and 35% of the total response, respectively, in ZIKV donors, whereas the NS3, NS4B and NS5 proteins have been reported to account for 31%, 15% and 22% of the DENV-specific T-cell response, respectively (Simmons C P, et al. 2005, J. Virol. 79(9):5665-5675; Duangchinda T, et al. 2010, Proc Natl Acad Sci USA 107(39):16922-16927; Rivino L, et al. 2013, J. Virol. 87(5):2693-2706; Weiskopf D, et al. 2013, Proc Natl Acad Sci USA 110(22):E2046-2053). As these donors were selected in DENV- and ZIKV-endemic areas, and as these viruses share an overall 43% protein sequence identity (with up to 68% for the non-structural proteins), the inventors sought to distinguish between the ZIKV-specific epitopes and those shared by both viruses. Among the 20 ZIKV-seropositive blood donors, 11 individuals had both anti-DENV and anti-ZIKV IgG antibodies and 9 individuals did not reveal any detectable anti-DENV antibodies (Table 1). The inventors thus analyzed separately T-cell responses from donors having only a history of ZIKV infection (ZIKV donors) and those from donors having a history of DENV and ZIKV infections (DENV/ZIKV donors). As shown in FIGS. 1 B and 1C, the NS1, NS3 and NS5 proteins accounted for 13%, 31% and 32% of the responses in ZIKV donors, respectively, whereas they accounted for 15%, 16% and 36% of the responses in DENV/ZIKV donors. These results confirmed that NS1, NS3 and NS5 were the main targets for T cells in ZIKV-infected donors, regardless of a previous infection with DENV, and revealed an increase in the frequency and magnitude of the response against NS5 in donors previously infected with DENV, in comparison with donors infected with ZIKV only.

From the 853 peptides spanning the entire ZIKV proteome, 410 peptides elicited a significant T-cell response, some of which being recognized by multiple donors. For most antigenic peptides, the HLA class I and class II alleles of the responding donors coincided with the alleles predicted to bind to this epitope (Andreatta M, et al. 2015, Immunogenetics 67(11-12):641-650; Nielsen M & Andreatta M 2016, Genome Med 8(1):33). Among the epitopes inducing a strong response in ZIKV and DENV/ZIKV donors, several 15-mer peptides contained short sequences predicted to bind strongly to at least one allele expressed by the responding donors (Table 2). For instance, the NS2B₃₁₁₇₋₁₃₁ peptide (having the amino acid sequence as defined in SEQ ID NO: 25) contained a 10-mer sequence (having the amino acid sequence as defined in SEQ ID NO: 26) predicted to bind strongly to the HLA-A*0301 and -A*1101 molecules expressed by the responding donor 55. In other cases, multiple responding donors expressed at least one common allele with strong potential for binding to the stimulating peptide. This hold for the E455-469 peptide (having the amino acid sequence as defined in SEQ ID NO: 7) in the envelope that contained the 9-mer (having the amino acid sequence as defined in SEQ ID NO: 9) and the 10-mer (having the amino acid sequence as defined in SEQ ID NO: 8) sequences predicted to bind to the HLA-B*5101 and HLA-A*0201 alleles, both alleles being expressed by the responding donors 1 and 77. This also applied to the NS5₁₃₋₂₇ peptide (having the amino acid sequence as defined in SEQ ID NO: 46), which induced a strong response in donors 55 and 69 that shared the HLA-B*3501 allele, this allele being predicted to bind to the 9-mer peptide MSALEFYSY (having the amino acid sequence as defined in SEQ ID NO: 47) with a high affinity. Interestingly, this epitope was also shown to induce a significant response in transgenic mice carrying the HLA-A*0101 molecule, which was expressed by donor 69 (Wen J, et al. 2017, Nat Microbiol 2:17036). Similarly, a strong T-cell response was observed against the NS5₅₄₆₋₅₆₀ peptide (having the amino acid sequence as defined in SEQ ID NO: 67) in donors 28, 53, and 66 that expressed the HLA-B*4002 and -B*4403 alleles and against the NS5₆₀₅₋₆₁₉ peptide (having the amino acid sequence as defined in SEQ ID NO: 72) in donors 33 and 59 that shared the predicted HLA-A*2402 allele. Finally, the inventors also identified several 9-mer immunodominant epitopes in the NS4B and NS5 proteins, included in the NS4B₁₁₂₋₁₂₆ (having the amino acid sequence as defined in SEQ ID NO: 41), the NS5₂₉₃₋₃₀₇ (having the amino acid sequences as defined in SEQ ID NOs: 49 and 50), NS5₂₉₇₋₃₁₁ (having the amino acid sequences as defined in SEQ ID NOs: 53-55) and NS5₃₄₅₋₃₅₉ (having the amino acid sequence as defined in SEQ ID NO: 58) peptides, which induced substantial T-cell responses in donors that shared one or several alleles with a strong potential for binding to these peptides.

Remarkably, among the NS3 and NS5 proteins, several epitopes have been already described as immunodominant epitopes, either predicted or validated experimentally after DENV infection or vaccination in humans or after ZIKV infection in mice (Wen J, et al. 2017, Nat Microbiol 2:17036; Dar H, et al. 2016, Asian Pac J Trop Med 9(9):844-850; Weiskopf D, et al. 2015, J. Virol. 89(1):120-128; Dikhit M R, et al. 2016, Infection, genetics and evolution: journal of molecular epidemiology and evolutionary genetics in infectious diseases 45:187-197). Indeed, among the 9-mer peptides identified in DENV/ZIKV donors, the NS5₂₉₃₋₃₀₇ (having the amino acid sequences as defined in SEQ ID NOs: 49 and 50), NS5₂₉₇₋₃₁₁ (having the amino acid sequences as defined in SEQ ID NOs: 53-55) and NS5₃₄₅₋₃₅₉ (having the amino acid sequence as defined in SEQ ID NO: 58) have been already detected in PBMCs from HLA-B*3501 individuals, after infection with DENV1, DENV2, or vaccination with DENV live attenuated vaccine (DLAV), with a lysine-to-arginine and a phenylalanine-to-tyrosine amino acid substitution at residues 302 and 350 in the NS5297-311 (having the amino acid sequences as defined in SEQ ID NOs: 53-55) and NS5₃₄₅₋₃₅₉ (having the amino acid sequence as defined in SEQ ID NO: 58) peptides from ZIKV, respectively (Rivino L, et al. 2013, J. Virol. 87(5):2693-2706; Weiskopf D, et al. 2015, J. Virol. 89(1):120-128; Imrie A, et al. 2007, J. Virol. 81(18):10081-10091) (Table 2). These results obtained from DENV/ZIKV donors thus confirmed that these NS5 peptides contained nested epitopes restricted by the HLA-B*3501 molecule. Yet the 15-mer NS3₂₁₉₋₂₃₃ peptide (having the amino acid sequence as defined in SEQ ID NO: 28), which contained the APTRVVAAEM epitope (having the amino acid sequence as defined in SEQ ID NO: 29), induced a substantial response in 2 DENV/ZIKV donors that expressed neither HLA-B*0702 nor B*3501, although these alleles were expressed in responding donors vaccinated with DLAV or in ifnar−/− HLA-B*0702 transgenic mice after ZIKV infection (Wen J, et al. 2017, Nat. Microbiol. 2:17036; Weiskopf D, et al. 2015, J. Virol. 89(1):120-128). This suggested that the NS3₂₁₉₋₂₃₃ peptide (having the amino acid sequence as defined in SEQ ID NO: 28) contained another epitope or a promiscuous epitope that bound to other HLA alleles, besides HLA-B*0702 or B*3501.

TABLE 2 Characteristics of antigenic peptides from ZIKV (having the amino acid sequences as defined in SEQ ID NOs: 1-75) identified in this study. SFC/million PBMC^(d) Predicted Predicted Score Peptide^(a) Sequence^(b) Donors HLA^(c) 15-mer 9-mer epitope HLA (rank)^(e) C₁₃₋₂₇ IVNM LKRGVARVS P 28 A02, 29; B40, 44; 170 <20 MLKRGVARV A0217 1.9 F C03, 16; DRB104, 07 60 A02, 69; B55, 58 50 60 A0205 1.3 C01, 07; DRB111, 13 C₈₅₋₉₉ KKDL AAMLRIIN AR 26 A02, 24; B07, 48; 100 <20 AAMLRIINA A0201 4.5 K C01, 07; DRB114, 15 60 A02, 69; B55, 58; <20 75 KDLAAMLRI B5501 1.4 C01, 07; DRB111, 13 K KDLAAMLRI INAR 28 A02, 29; B40, 44; 230 65 B4002 2.0 K C03, 16; DRB104, 07 E₄₅₅₋₄₆₉ GMSWFSQILIGTLL  1 A02, 24; B35, 51; 120 NT GMSWFSQILI A0201 0.9 M C01, 01; DRB104, 12 77 A02, 02; B40, 51; 35 NT MSWFSQILI B5101 0.12 C04, 07; DRB113, 14 NS1₆₃₋₇₇ MEN IMWRSVEGE LN 21 A31, 03; B35, 18; 65 50 MENIMWRSVEGELNA DRB10405 50 A C01, 17; DRB104, 03 MENIM WRSVEGELN 28 A02, 29; B40, 44; 245 58 IMWRSVEGEL A0217 0.5 A C03, 16; DRB104, 07 56 A02, 02; B15, 18; 70 148 A0201 1.2 C05, 07; DRB103, 11 NS1₈₃₋₉₇ G VQLTVVVGS VKNP 26 A02, 24; B07, 48; 145 23 VQLTVVVGSV A0201 1.7 M C01, 07; DRB114, 15 28 A02, 29; B40, 44; 165 35 A0217 3 C03, 16; DRB104, 07 NS1₁₆₃₋₁₇₇ FHTS VWLKVREDY S 28 A02, 29; B40, 44; 230 75 HTSVWLKVREDY A0101 0.4 L C03, 16; DRB104, 07 FHTSV WLKVREDYS 55 A03, 11; B35, 51; 110 125 HTSVWLKVR A3101 0.4 L C04, 15; DRB101, 07 46 A32, 68; B39, 50; 50 32 A6801 0.6 C06, 07; DRB104, 07 20 A01, 31; B07, 39; 310 105 VWLKVREDY A2902 1.3 C07, 07; DRB104, 15 FHTSVWLKV B3905 0.4 B3901 0.4 NS1₂₇₅₋₂₈₉ IRFEE CPGTKVHVE 33 A24, 24; V15, 35; 215 55 CPGTKVHVE B3501 8.5 E C01, 03; DRB104, 04 55 A03, 11; B35, 51; 130 115 B3531 6.5 C04, 15; DRB101, 07 NS2B₁₁₇₋₁₃₁ AAGAWYVYVKTGKR 55 A03, 11; B35, 51; 445 NT AAGAWYVYVK A0301 0.6 S C04, 15; DRB101, 07 A1101 0.12 YVYVKTKGR A0301 1.8 NS3₂₁₉₋₂₃₃ TVILAPTRVVAAEM 53 A23, 31; B40, 44; 100 NT TVILAPTRVVAAEME DRB10802 1.5 E C01, 04; DRB107, 08 66 A02, 03; B39, 40; 65 NT ILAPTRVVAA A0201 1.6 C03, 07; DRB108, 15 NS3₂₇₁₋₂₈₅ LQPIRVPNYNLYIM 42 A26, 26; B35, 38; 165 NT VPNYNLYIM B3501 0.06 D C05, 06; DRB104, 11 NS3₃₁₁₋₃₂₅ AAI FMTATPPGT RD 28 A02, 29; B40, 44; 255 85 AAIFMTATPPGTRDA DRB10401 4 A C03, 16; DRB104, 07 FMTATPPGT A0217 5.5 AA IFMTATPPG TRD 33 A24, 24; B15, 35; 215 30 IFMTATPPG A2402 5 A C01, 03; DRB104, 04 60 A02, 69; B55, 58; 125 NT VTLGASAWL A6901 1.3 C01, 07; DRB111,13 LGASAWLMW B5801 0.07 NS4B₁₁₂₋₁₂₆ AIILLVAHY MYLIP 28 A02, 29; B40, 44; 60 58 AIILLVAHY A2902 0.6 G C03, 16; DRB104, 07 37 A02, 11; B35, 50; 75 30 A1101 3.5 C04, 06; DRB101, 13 AII LLVAHYMYLI P 60 A02, 69; B55, 58; 100 68 LLVAHYMYL A0205 0.3 G C01, 07; DRB111, 13 AIIL LVAHYMYL IP 60 A02, 69; B55, 58; 100 35 LVAHYMYLI A6901 0.15 G C01, 07; DRB111, 13 A0205 0.2 NS5₁₃₋₂₇ KARLNQMSALEFYS 55 A03, 11; B35, 51; 260 NT MSALEFYSY B3501 0.15 Y C04, 15; DRB101, 07 69 A01, 24; B35, 35; 145 NT A0101 0.09 C01, 04; DRB014, 13 NS5₂₉₃₋₃₀₇ WFFDEN HPYRTWAY 55 A03, 11; B35, 51; 1580 308 HPYRTWAYH B3501 0.4 H C04, 15; DRB101, 07 W FFDENHPYR TWAY 69 A01, 24; B35, 35; 40 218 FFDENHPY A0101 1.6 H C01, 04; DRB104, 13 NS5₂₉₇₋₃₁₁ E NHPYRTWAY HGSY 55 A03, 11; B35, 51; 1280 358 NHPYRTWAY B3501 3 E C04, 15; DRB101, 07 ENHP YRTWAYHGS Y 69 A01, 24; B35, 35; 75 188 YRTWAYHGSY B3501 1.7 E C01, 04; DRB104, 13 A0101 0.3 ENHPY RTWAYHGSY 69 A01, 24; B35, 35; 75 205 RTWAYHGSY A0101 0.5 E C01, 04; DRB104, 13 NS5₃₄₅₋₃₅₉ TDT TPYGQQRVF KE 33 A24, 24; B15, 35; 1315 395 TPYGQQRVF B3531 0.7 K C01, 03; DRB104, 04 55 A03, 11; B35, 51; 2095 523 B3501 0.3 C04, 15; DRB101, 07 69 A01, 24; B35, 35; 785 763 C01, 04; DRB104, 13 NS5₄₂₅₋₄₃₉ EAVNDPRFW ALVDK 28 A02, 29; B40, 44; 150 100 AVNDPRFWALVDK A0301 1.1 E C03, 16; DRB104, 07 55 A03, 11; B35, 51; 120 125 A1101 0.6 C04, 51; DRB101, 07 56 A02, 02; B15, 18; 90 240 C05, 07; DRB103, 11 NS5₄₆₁₋₄₇₅ KKQGEFGKAKGSRA 28 A02, 29; B40, 44; 300 NT KKQGEFGKAKGSRAI DRB10701 32 I C03, 16; DRB104, 07 53 A32, 31; B40, 44; 105 NT GEFGKAKGSRAI B4002 0.7 C01, 04; DRB107, 08 NS5₄₇₃₋₄₈₇ RAIWYMWLGARFLE 28 A02, 29; B40, 44; 210 NT YMWLGARFL A0217 0.03 F C03, 16; DRB104, 07 55 A03, 11; B35, 51; 295 NT AIWYMWLGAR A0301 1.3 C04, 15; DRB101, 07 RAIWYMWLGARFLEF DRB10701 16 NS5₅₄₆₋₅₆₀ RFDLENEALITNQM 28 A02, 29; B40, 44; 245 NT NEALITNQM B4002 0.8 E C03, 16; DRB104, 07 53 A23, 31; B40, 44; 190 NT B4003 0.6 C01, 04; DRB107, 08 66 A02, 03; B39, 40; 80 NT B3901 1.8 C03, 07; DRB108, 15 NS5₅₆₅₋₅₇₉ LALAIIKYTYQNKV 28 A02, 29; B40, 44; 240 NT LALAIIKYTY A2902 0.5 V C03, 16; DEB104,07 53 A23, 31; B40, 44; 120 NT ALAIIKYTY A2902 0.25 C01, 04; DRB107; 09 56 A02, 02; B15, 18; 150 NT LALAIIKYTY B1517 1.2 C05, 07; DRB103, 11 NS5₆₀₅₋₆₁₉ QVVTYALNTFTNLV 33 A24, 24; B15, 35; 240 NT TYALNTFTNL A24:02 0.09 V C01, 03; DRB104, 04 59 A03, 24; B35, 40; 50 42 YALNTFTNL B35:43 0.4 C10, 03; DRB104, 04 B35:31 0.25 *The position of peptides were determined according to NCBI Reference Sequence YP_002790881.1; ^(†)The underlined and in bold sequence correspond to the 9-mer peptide tested; ^(‡)The common alleles between donors are underlined and in bold; ^(§)Cumulative SFC/million PBMC; NT, not tested; ^(¶)Calculated using NetMHCpan 3.0 and NetMHCIIpan3.1 servers: for MHC class I, strong binders <0.5, weak binders <2. Broader Responses with a Higher Magnitude in Donors with Previous DENV Infection

Given the ZIKV-specific antibody response against NS1 and the low level of CD4 T-cell cross-reactivity between DENV and ZIKV against the E and NS1 proteins (Stettler K, et al. 2016, Science 353(6301):823-826), the inventors compared, among the immunodominant epitopes, the T-cell responses in PBMCs from ZIKV donors with those from DENV/ZIKV donors. First, comparison of the frequency of responding T cells in ZIKV and DENV/ZIKV donors underlined the higher magnitude of response in DENV/ZIKV donors, relative to ZIKV donors (FIGS. 1B and 1C). The number of stimulating peptides per donor, as well as the average response per donor differed in these two groups, with a significantly broader response and a higher magnitude of response in donors with previous DENV infection (FIG. 2A, left and right panels). To determine whether this difference concerned only a small number of peptides that elicited a stronger response in each donor, or if it concerned the majority of the peptides, the inventors plotted the frequency of responses against the different peptides, per donor, in the two different groups. As shown in FIG. 2B, two out of nine individuals among the ZIKV donors revealed a median response higher than 100 SFC/million cells, whereas six out of eleven DENV/ZIKV donors developed this strong response, which was also directed against a higher number of peptides. This result revealed the activation of a higher frequency of T cells against ZIKV peptides, with a higher magnitude of response, in donors previously infected with DENV, in comparison with naïve donors. This strongly argued for the existence of cross-reactive T cells, these T cells being primed during the initial infection with DENV and expanded thereafter during the following infection with ZIKV, as shown recently in mice after sequential infection with DENV and ZIKV (Wen J, et al. 2017, Nat Microbiol 2:17036).

DENV/ZIKV-Cross-Reactive T Cells Mainly Target the NS5 Protein

To identify more specifically ZIKV-specific peptides and DENV/ZIKV cross-reactive peptides, the inventors compared the sequences of the most immunodominant epitopes recognized by both types of donors. As shown in FIG. 2A and Table 3, NS1 and NS3 proteins contained a high proportion of peptides that elicited strong responses in both ZIKV and DENV/ZIKV donors, whereas the E protein and to a higher extent the NS5 protein contained a majority of peptides inducing a strong response only in DENV/ZIKV donors. This suggested that the NS1 and NS3 proteins contained more ZIKV-specific epitopes, whereas the NS5 protein contained more epitopes shared by DENV and ZIKV and recognized by cross-reactive T cells. Strikingly, most of the peptides recognized only by DENV/ZIKV donors exhibited high degree of identity with the four DENV serotypes. For instance, in the NS1 protein, two out of the five epitopes that induced a response in ZIKV donors revealed a sequence identity higher than 60% with the four DENV serotypes, whereas eight out of the eleven epitopes in the NS5 protein that induced a strong response in DENV/ZIKV donors showed a sequence identity higher than 66.7% with the four DENV serotypes (Table 3). To determine whether the increased magnitude of response was correlated with the recognition of peptides having a higher sequence identity with DENV, the inventors plotted the cumulative responses for each peptide against the percentage of identity between DENV and ZIKV sequences. Among the ZIKV donors, only four ZIKV peptides with about 60% identity with DENV could elicit a response higher than 300 SFC per million cells, whereas twenty-one ZIKV peptides with at least 70% identity with DENV induced this strong response in DENV/ZIKV donors (FIG. 3); the four peptides inducing the strongest T-cell response in these donors shared the highest sequence identity with DENV. Altogether, these data strongly supported the activation of cross-reactive T cells induced after DENV and ZIKV infections, which recognized common epitopes between DENV and ZIKV, and dominated the T-cell response against ZIKV.

TABLE 3 Immunodominant epitopes in ZIKV and DENV/ZIKV donors (having the amino acid sequences as defined in SEQ ID NOs: 17, 25, 46, 48, 52, 57, 62, 64, 67 and 76-93) ZIKV DENV/ZIKV SFC/ SFC/ million million % Identity Peptide^(a) Sequence Donors PBMC^(b) Donors PBMC^(b) DENV1 DENV2 DENV3 DENV4 C₄₉₋₆₃ AILAFLRFTAIKPSL 60  60 28, 63  365  60.0%  53.3%  60.0%  40.0% E₆₇₋₈₁ DMASDSRCPTQGEAY 33  465  66.7%  53.3%  66.7%  53.3% E₈₇₋₁₀₁ DTQYVCKRTLVDRGW 56  505  66.7%  53.8%  73.3%  66.7% NS1₁₉₋₃₃ VFVYNDVEAWRDRYK 21, 46, 60 195 28, 56  380  46.7%  33.3%  46.7%  40.0% NS1₅₅₋₆₉ CGISSVSRMENIMWR 35, 46 125 56  275  67.1%  66.3%  60.0%  60.0% NS1₉₁₋₁₀₅ GSVKNPMWRGPQRLP 21, 35, 46, 60 275 28  165  13.3%  33.3%  20.0%  33.3% NS1₁₀₇₋₁₂₁ PVNELPHGWKAWGKS 28, 53  430  40.0%  46.7%  46.7%  50.5% NS1₁₄₇₋₁₆₁ HRAWNSFLVEDHGFG 46  40 33, 53  445  66.7%  73.3%  66.7%  76.2% NS1₁₆₃₋₁₇₇ FHTSVWLKVREDYSL 46  35 20, 28, 55  450  46.7%  46.3%  53.3%  46.7% NS1₁₉₅₋₂₀₉ HSDLGYWIESEKNDT 28, 33  615  80.0%  73.3%  66.2%  73.3% NS2B₁₁₇₋₁₃₁ AAGAWYVYVKTGKRS 55  445  33.3%  33.3%  26.7%  26.7% NS3₁₃₁₋₄₄₅ PAGTSGSPILDKCGR 21, 42 405 26, 55, 63  495  53.3%  60,8%  53.3%  54.3% NS3₁₄₃₋₁₅₇ CGRVIGLYGNGVVIK 21 350 20, 55, 63, 66  550  60.0%  66.7%  72.3%  80.0% NS3₃₁₁₋₃₂₅ AAIFMTATPPGTRDA 28, 33  470  80.0%  80.0%  93.3%  80.0% NS5₁₃₋₂₇ KARLNQMSALEFYSY 55, 69  405  53.3%  46.7%  53.3%  40.0% NS5₂₉₃₋₃₀₇ WFFDENHPYRTWAYH 55, 69 1620  66.7%  66.7%  60.0%  66.7% NS5₂₉₇₋₃₁₁ ENHPYRTWAYHGSYE 55, 69 1330  80.0%  80.0%  73.3%  80.0% NS5₃₂₅₋₃₃₉ VVRLLSKPWDVVTGV 28, 55, 66  495  73.3%  80.0%  73.3%  66.7% NS5₃₄₅₋₃₅₉ TDTTPYGQQRVFKEK 33, 55, 69 4195  93.3%  93.3%  93.3%  93.3% NS5₃₇₃₋₃₈₇ QVMSMVSSWLWKELG 60 130 55, 66, 69  340  40.0%  53.3%  46.7%  46.7% NS5₄₆₁₋₄₇₅ KKQGEFGKAKGSRAI 28, 53  405  93.3%  93.3%  93.3%  86.7% NS5₄₆₅₋₄₇₉ EFGKAKGSRAIWYMW 28, 53, 55, 56 1085 100.0% 100.0% 100.0%  93.3% NS5₄₇₃₋₄₈₇ RAIWYMWLGARFLEF 28, 55  505 100.0% 100.0%  93.3% 100.0% NS5₄₈₁₋₄₉₅ GARFLEFEALGFLNE 28, 53, 56, 63 1870  93.3% 100.0%  93.3% 100.0% NS5₅₄₆₋₅₆₀ RFDLENEALITNQME 28, 53, 66  515  60.0%  47.1%  53.3%  60.0% NS5₅₇₃₋₅₈₆ TYQNKVVKVERPAEK 28, 53, 56  615  72.9%  66.7%  73.3%  80.0% NS5₈₄₉₋₈₆₃ CGSLIGHRPRTTWAE 60  90 33, 55  340  66.7%  66.7%  66.7%  66.7% ^(†)Cumulative SFC/million PBMC *The position of peptides were determined according to NCBI Reference Sequence YP_002790881.1

In this study, using PBMCs from ZIKV-infected human blood donors, the inventors identified numerous T-cell epitopes that were specific to ZIKV or shared between DENV and ZIKV. While the DENV-specific T-cell responses are predominantly directed against NS3, NS4B and NS5, the response against ZIKV mainly targeted epitopes in the NS1, NS3 and NS5 proteins. The stronger and broader IFN-γ response against peptides from the NS5 protein, observed in donors previously infected with DENV, led the inventors to postulate that this region contained more peptides recognized by cross-reactive T cells, whereas the NS1 protein was preferentially targeted by ZIKV-specific T cells. These data were consistent with the higher percentage of identity observed between ZIKV and DENV sequences in the NS5 protein, in comparison with the NS1 protein. In addition to its sequence identity, the high NS1 secretability observed with the Asian lineages of ZIKV (Liu Y, et al. 2017, Nature 545 (7655): 482-486) could also explain the higher frequency of NS1-specific T cells induced in ZIKV-infected donors, in comparison with the frequency of NS1-specific T cells observed in DENV-infected donors (Weiskopf D, et al. 2013, Proc Natl Acad Sci USA 110(22):E2046-2053).

For several epitopes, the 15-mer or 9-mer peptides matched epitopes recently identified in transgenic mice expressing human HLA molecules, thus confirming the class I allele restriction for this peptide. This was the case for 15-mer peptide VARVSPFGGLKRLPA (having the amino acid sequence as defined in SEQ ID NO: 92) inducing a response in a donor expressing the HLA-B*0702 allele (data not shown), which contained the C25-35 peptide SPFGGLKRLPA (having the amino acid sequence as defined in SEQ ID NO: 93) shown to elicit a significant response in HLA-B*0702 transgenic mice infected with ZIKV (Wen J, et al. 2017, Nat Microbiol 2:17036). The same correlations were established with NS3 (FPDSNSPIM, having the amino acid sequence as defined in SEQ ID NO: 94), NS4B (RGSYLAGASLIYTVT, having the amino acid sequence as defined in SEQ ID NO: 95) and NS5 (NQMSALEFYSY, having the amino acid sequence as defined in SEQ ID NO: 96) peptides that induced a strong response in human donors expressing the HLA-B*0702 and HLA-A*0101 alleles, respectively (data not shown and Table 2), and in transgenic mice expressing these alleles (Wen J, et al. 2017, Nat Microbiol 2:17036). In other cases, the epitopes identified in HLA-B*0702 and HLA-A*0101 transgenic mice were also identified in responding donors that nevertheless did not express these alleles, such as the NS3₂₁₉₋₂₃₃ peptide (having the amino acid sequence as defined in SEQ ID NO: 28) (Table 2) and the NS1₁₉₋₃₃ (having the amino acid sequence as defined in SEQ ID NO: 78) or the NS5₅₁₃₋₂₇ (having the amino acid sequence as defined in SEQ ID NO: 46) peptides (Table 3), which elicited a response in donors that expressed neither of the two alleles, HLA-B*0702 or HLA-A*0101. For these donors, one possibility could be that the epitope identified in transgenic mice had a higher affinity for a human HLA allele different from the allele expressed by the transgenic mice, or that the 15-mer peptide contained another epitope that bound to a different allele. Binding studies with 9-mer epitopes and HLA class I stabilization assays using TAP-deficient cells should discriminate between these possibilities.

The inventors also reported the identification of several peptides that shared common sequences with DENV and were preferentially targeted by cross-reactive T cells, after DENV and ZIKV infection. Among these peptides, the NS5₂₉₃₋₃₀₇ (having the amino acid sequence as defined in SEQ ID NO: 48) and NS5₂₉₇₋₃₁₁ (having the amino acid sequence as defined in SEQ ID NO: 52) peptides contained the amino acid sequence HPYRTWAYH (having the amino acid sequence as defined in SEQ ID NO: 49), which shared seven amino acids with an epitope previously identified in Pacific Islanders infected with DENV1 (Imrie A, et al. 2007, J. Virol. 81(18):10081-10091). Similarly, the NS5₃₂₅₋₃₃₉ (having the amino acid sequence as defined in SEQ ID NO: 86) peptide contained the amino acid sequence KPWDWTGV (having the amino acid sequence as defined in SEQ ID NO: 97), which was also 66.7% identical to the epitope KPWDVIPMV (having the amino acid sequence as defined in SEQ ID NO: 98) identified in these individuals infected with DENV1 (Imrie A, et al. 2007 J. Virol. 81(18):10081-10091). Finally, the NS5345-359 (having the amino acid sequence as defined in SEQ ID NO: 58), NS5₄₆₅₋₄₇₉ (having the amino acid sequence as defined in SEQ ID NO: 88) and NS5₄₈₁₋₄₉₅ (having the amino acid sequence as defined in SEQ ID NO: 89) peptides inducing the strongest response in DENV/ZIKV donors (Table 3) also contained 9-mer epitopes that were previously identified in DENV-infected individuals (Weiskopf D, et al. 2015, J. Virol. 89(1):120-128). Altogether, these data revealed the activation of DENV/ZIKV cross-reactive T cells that dominated the response following sequential DENV and ZIKV infections. Notably, although these cross-reactive peptides exhibited a high degree of sequence identity with DENV and could stimulate a T-cell response after DENV infection, these peptides did not induce a response after primary infection with ZIKV, suggesting that these peptides were immunodominant in the context of DENV but not in the context of ZIKV infection. This result was expected, as the immunodominance of an epitope or its relative abundance depends on the other epitopes expressed by the protein. This was also in agreement with previous observations showing that epitope production correlated with cleavability of flanking residues expressed in the protein sequence (Zhang S C, et al. 2012, J. Immunol. 188(12):5924-5934). Importantly, for these cross-reactive epitopes, the absence of a T-cell response in ZIKV-infected donors was not simply due to the absence of the presenting HLA allele in this population, as most of the alleles expressed in responding DENV/ZIKV donors were also expressed in ZIKV donors (Table 1). This is what the inventors observed for the NS5₁₃₋₂₇ (having the amino acid sequence as defined in SEQ ID NO: 46), NS5₂₉₃₋₃₀₇ (having the amino acid sequence as defined in SEQ ID NO: 48), NS5₃₄₅₋₃₅₉ (having the amino acid sequence as defined in SEQ ID NO: 57) and NS5₅₄₆₋₅₆₀ (having the amino acid sequence as defined in SEQ ID NO: 67) epitopes, predicted to be strong binders to the HLA-B*3501 and HLA-B*4002 alleles, respectively, that were frequently expressed by ZIKV donors (Table 2 and FIG. 3). Altogether, these results showed that, in the case of initial ZIKV infection, there was a preferential recognition of ZIKV-specific epitopes, whereas there was a more frequent and stronger T-cell response against cross-reactive epitopes after heterologous DENV/ZIKV infection. Interestingly, the strong T-cell response observed in DENV/ZIKV donors against these NS5 epitopes relied primarily on donors that expressed the HLA-B*3501 allele, an allele associated with high magnitude responses against DENV, and a stronger protection against DENV infection and disease (Weiskopf D, et al. 2013, Proc Natl Acad Sci USA 110(22):E2046-2053). As all blood samples were obtained from donors with asymptomatic ZIKV infection history, the inventors could not relate the strength of the ZIKV-specific T-cell response obtained in HLA-B*3501 donors to the protection against the disease. Further studies with more subjects with a higher susceptibility to disease following primary ZIKV infection are required to determine whether, as for DENV, there is an HLA-linked protective role for T cells in ZIKV infection. Likewise, it would also be important to compare disease severity in donors having or not experienced a previous DENV infection, to determine whether cross-reactive T cells induced after DENV infection could mediate a better protection against ZIKV infection and disease, as recently suggested in mice (Wen J, et al. 2017, Nat Microbiol 2:17036; Elong Ngono A, et al. 2017, Cell host & microbe 21(1):35-46). As both CD4+ and CD8+ T cells were shown to contribute to protection against DENV infection, a comprehensive analysis of MHC class II-restricted response is needed to determine the role of CD4 in ZIKV infection and disease protection. Finally, further phenotypic analyses of ZIKV-specific T cells, in asymptomatic or symptomatic donors will help in defining correlates of protection in natural immunity and vaccination against ZIKV infection and disease. It will be particularly important to determine whether, as for DENV-specific T cells, strong responses against ZIKV-specific peptides are more frequent in specific HLA alleles and are associated with multifunctionality (Weiskopf D, et al. 2013, Proc Natl Acad Sci USA 110(22):E2046-2053).

In conclusion, while many studies have focused on the antibody response against ZIKV, more specifically the identification of B cell epitopes shared between ZIKV and DENV, little is known regarding the role of T cells in the control of ZIKV infection. Using PBMCs from blood donors with recent history of ZIKV infection, seropositive or not for DENV, the inventors established the first map of the distribution of ZIKV T-cell epitopes by screening the complete proteome by interferon (IFN)-y enzyme-linked immunospot (ELISPOT) assay. The inventors showed that the non-structural proteins NS1, NS3 and NS5 contained most of the immunodominant peptides that induced a strong T-cell response. The inventors also showed that the NS5 protein contained many epitopes shared by both viruses, and which induced the highest response following DENV and ZIKV infections. Strikingly, donors with a history of DENV infection revealed a substantial response against peptides previously identified as DENV CD8+ T-cell epitopes. The strongest T-cell responses observed in these donors corresponded to sequences with a high level of amino acid identity with the four DENV serotypes, suggesting the activation of cross-reactive T cells. These results have crucial implications for future ZIKV and DENV vaccines and provide new opportunities to study the role of ZIKV-specific and DENV/ZIKV shared T-cell epitopes in the induction of long-term immunity against these viruses.

Poly-ZIKV DNA Vaccination in Mice

DNA immunization will be performed using plasmid coding for the chimeric polyepitope and electroporation, with 2×50 μg DNA, at 3 weeks interval and challenge 15 days after the boost with the virus (intraperitoneal injection of ZIKV with 10³ pfu/mouse).

DNA vaccination with plasmids and electroporation (EP) will be performed as follows:

For vaccination, two injections of 25 μl each of DNA at 2 mg/ml will be performed by intradermal inoculation in the back, followed immediately by electroporation using AgilePulse apparatus (BTX Harvard Apparatus).

The electroporation procedure will consist of 3 voltage groups: Group 1: 450V, pulse length 50 μsec, pulse interval of 0.2 μsec, Nb pulses: 1; Group 2: 450V, pulse length 50 μsec, pulse interval of 50 μsec, Nb pulses: 1; Group 3: 110V, pulse length 10 msec, pulse interval of 20 msec, Nb pulses: 8.

At day −1 before the challenge with ZIKV, intraperitoneal injection with 2 mg anti-IFNAR antibody (MAR1-5A3) will be performed to transiently block the IFN type I response.

The viremia will be quantified by qRT-PCR in plasma samples from day 1 to day 6 after the challenge.

DNA vaccination in Non-Human Primates (Indian Rhesus Macaques Monkeys)

DNA vaccination will be performed by 2 intramuscular injections with 1 mg plasmid coding for the chimeric polyepitope of ZIKV, at 0 and 4 weeks, followed by a challenge 4 weeks later by inoculating subcutaneously 10⁴ pfu ZIKV, as previously described (Dowd, K. A., et al. Science 2016, 354, 237-240).

PBMC will be collected at day 0 (before the prime), day 7 after the prime, then at day 35 (one week after the boost) and day 60 (before challenge with ZIKV), to analyse the T cell response (IFN-γ and TNF-α) by ELISpot against overlapping peptides covering the whole chimeric polyepitope sequence. The number and phenotype of Monocytes CD14, DCs, T cells, B cells, and NK cells, and the cytokine profile of T cells (CD8 T cells) will be analysed by intracellular staining.

Blood samples will also be collected at day 0 (prior to immunization), day 14, day 28 (prior to boost) and day 56 (prior to challenge) to determine neutralizing Ab titres by Focus Reduction Neutralization Titres (FRNT).

Plasma samples will be tested for quantification of viremia by qRT-PCR, daily from day 56 (prior to challenge) until day 66.

Alternate Protocol Using DNA Vaccination with Plasmids Expressing Cytokines, as Genetic Adjuvants to Remove the Electroporation

Recent studies have shown that co-administration of plasmids expressing T cell epitopes with plasmids expressing either IL-12, or GM-CSF, or a combination of both IL-12 and GM-CSF improves the T cell response, sufficiently to remove the need for electroporation (EP) (Boyer, J. D., et al. J Med Primatol 2005, 34, 262-270; Suschak, J. J., et al. The Journal of infectious diseases 2018; Suschak, J. J., et al. Antiviral research 2018, 159, 113-121).

The inventors will thus assess the effect of IL-12 and GM-CSF DNA immunization combined with Poly-ZIKV DNA immunization on the magnitude of T cell response against ZIKV peptides and the immune protection against ZIKV infection in Rhesus monkeys. 

1-24. (canceled)
 25. A chimeric polyepitope comprising (i) at least the following T-cell epitopes of (a) and (b), or (ii) at least the following T-cell epitopes of (a) and (c), or (iii) at least the following T-cell epitopes of (b) and (c): (a) a T-cell epitope of the non-structural (NS) NS1 protein of a Zika virus (ZIKV) comprising or consisting of an amino acid sequence selected from the group consisting of SEQ ID NOs: 10-12, 14, 15, 17-19, 23, 24 and 78-83, (b) a T-cell epitope of the NS3 protein of a ZIKV comprising or consisting of an amino acid sequence selected from the group consisting of SEQ ID NOs: 28, 29, 31, 33-35, 84 and 85, (c) a T-cell epitope of the NS5 protein of a ZIKV comprising or consisting of an amino acid sequence selected from the group consisting of SEQ ID NOs: 46, 48-50, 52-55, 57-60, 62, 64, 67, 69, 72, 73 and 86-91, or a T-cell epitope variant thereof, which differs from the original amino acid sequence of the T-cell epitope of (a), (b) or (c) by point mutation of one or more amino acid residues and which has at least 90% sequence identity or more than 95% sequence identity or 99% sequence identity with said original sequence.
 26. The chimeric polyepitope according to claim 25, comprising at least the T-cell epitopes of (a), (b) and (c), or the T-cell epitope variant thereof.
 27. The chimeric polyepitope according to claim 25, consisting of (i) the T-cell epitopes of (a) and (b), or (ii) the T-cell epitopes of (a) and (c), or (iii) the T-cell epitopes of (b) and (c), or (iv) the T-cell epitopes of (a), (b) and (c), or the T-cell epitope variant thereof.
 28. The chimeric polyepitope according to claim 25, wherein the T-cell epitope of (a) comprises or consists of the amino acid sequence selected from the group consisting of SEQ ID NOs: 17, 23 and 78-83, the T-cell epitope of (b) comprises or consists of the amino acid sequence selected from the group consisting of SEQ ID NOs: 31, 33, 84 and 85, and the T-cell epitope of (c) comprises or consists of the amino acid sequence selected from the group consisting of SEQ ID NOs: 46, 48, 52, 57, 62, 64, 67 and 86-91.
 29. The chimeric polyepitope according to claim 25, wherein the T-cell epitope of (a) comprises or consists of the amino acid sequence of SEQ ID NOs: 11, 12, 17-19, 23, 24, 78, 80 and 83, the T-cell epitope of (b) comprises or consists of the amino acid sequence of SEQ ID NOs: 28, 31, 33, 34, 84 and 85, and the T-cell epitope of (c) comprises or consists of the amino acid sequence of SEQ ID NOs: 48-50, 52-55, 57, 58, 60, 62, 67, 88, 89 and
 90. 30. The chimeric polyepitope according to claim 25, further comprising at least one T-cell epitope of a ZIKV protein selected from the group consisting of: (i) a T-cell epitope of the C protein of a ZIKV comprising or consisting of an amino acid sequence selected from the group consisting of SEQ ID NOs: 1, 2, 4-6 and 75, (ii) a T-cell epitope of the E protein of a ZIKV comprising or consisting of an amino acid sequence selected from the group consisting of SEQ ID NOs: 7, 76 and 77, (iii) a T-cell epitope of the NS2B protein of a ZIKV comprising or consisting of the amino acid sequence of SEQ ID NO: 25, (iv) a T-cell epitope of the NS4A protein of a ZIKV comprising or consisting of the amino acid sequence of SEQ ID NO: 36, and (v) a T-cell epitope of the NS4B protein of a ZIKV comprising or consisting of the amino acid sequence selected from the group consisting of SEQ ID NOs: 40-43.
 31. The chimeric polyepitope according to claim 30, wherein said at least one T-cell epitope of a ZIKV protein is selected from the group consisting of: the T-cell epitope of the C protein of a ZIKV comprising or consisting of an amino acid sequence selected from the group consisting of SEQ ID NOs: 1, 2, 4-6 and 75, and the T-cell epitope of the NS4B protein of a ZIKV comprising or consisting of the amino acid sequence selected from the group consisting of SEQ ID NOs: 40-43.
 32. The chimeric polyepitope according to claim 31, which has an amino acid sequence of SEQ ID NO:
 99. 33. The chimeric polyepitope according to claim 25, which elicits a human leukocyte antigen (HLA)-restricted CD8+ and/or CD4+ T cell response (i) against ZIKV, or (ii) against ZIKV and DENV, in particular DENV serotype 1 (DENV1), DENV serotype 2 (DENV2), DENV serotype 3 (DENV3) and DENV serotype 4 (DENV4).
 34. The chimeric polyepitope according to claim 25, wherein the T-cell epitopes are assembled in a fusion polypeptide.
 35. The chimeric polyepitope according claim 25, wherein the ZIKV is from the African lineage, or from the Asian lineage.
 36. An isolated or purified polynucleotide encoding the chimeric polyepitope according to claim
 25. 37. A vector comprising the polynucleotide according to claim
 36. 38. Transformed eukaryotic cells comprising the polynucleotide according to claim
 36. 39. An immunogenic composition comprising the chimeric polyepitope according to claim 25, and an adjuvant and/or a pharmaceutically acceptable vehicle.
 40. The immunogenic composition according to claim 39, wherein said composition is formulated for an administration by a route selected from the group consisting of subcutaneous (s.c.), intradermal (i.d.), intramuscular (i.m.), intraperitoneal (i.p.) and intravenous (i.v.) injection.
 41. The immunogenic composition according to claim 39, formulated for administration in a prime-boost administration regime.
 42. A method of (i) preventing a Zika virus (ZIKV) infection in a human subject or (ii) preventing ZIKV and Dengue virus (DENV) infections in a human subject, comprising administering the chimeric polyepitope according to claim 25 to the human subject.
 43. The method of preventing a ZIKV infection in a human subject according to claim 42, wherein the T-cell epitopes are ZIKV-specific epitopes comprising or consisting of an amino acid sequence selected from the group consisting of SEQ ID NOs: 1, 2, 5, 10, 11, 19, 27, 31, 40-43, 46, 72, 73, 75, 78-80, 82, 84, 85, 87 and
 91. 44. The method of preventing ZIKV and DENV infections in a human subject according to claim 42, wherein the T-cell epitopes are ZIKV-DENV cross-reactive epitopes comprising or consisting of an amino acid sequence selected from the group consisting of SEQ ID NOs: 1, 5, 6, 12, 14, 15, 17-19, 23, 24, 27, 28, 33-35, 40, 41, 46, 48-50, 52-55, 57, 59, 60, 62, 64, 67, 69, 72, 73, 84, 85 and 86-91. 